#!/usr/bin/env python3
# coding=utf-8
#
# Copyright (C) 2011 Nikita Kitaev
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
#
"""
An Inkscape extension for exporting Synfig files (.sif)
"""
import math
import uuid
from copy import deepcopy

from lxml import etree

import inkex
from inkex import (
    Group,
    Layer,
    Anchor,
    Switch,
    PathElement,
    Metadata,
    NamedView,
    Gradient,
    SvgDocumentElement,
    Path,
    Transform,
    OutputExtension,
)

import synfig_fileformat as sif
from synfig_prepare import *


# ##### Utility Classes ####################################
class UnsupportedException(Exception):
    """When part of an element is not supported, this exception is raised to invalidate the whole element"""

    pass


class SynfigDocument(object):
    """A synfig document, with commands for adding layers and layer parameters"""

    def __init__(self, width=1024, height=768, name="Synfig Animation 1"):
        self.root_canvas = etree.fromstring(
            """
    <canvas
        version="0.5"
        width="{:f}"
        height="{:f}"
        xres="2834.645752"
        yres="2834.645752"
        view-box="0 0 0 0"
        >
      <name>{}</name>
    </canvas>
    """.format(
                width, height, name
            )
        )

        self._update_viewbox()

        self.gradients = {}
        self.filters = {}

    # ## Properties

    def get_root_canvas(self):
        return self.root_canvas

    def get_root_tree(self):
        return self.root_canvas.getroottree()

    def _update_viewbox(self):
        """Update the viewbox to match document width and height"""
        attr_viewbox = "{:f} {:f} {:f} {:f}".format(
            -self.width / 2.0 / sif.kux,
            self.height / 2.0 / sif.kux,
            self.width / 2.0 / sif.kux,
            -self.height / 2.0 / sif.kux,
        )
        self.root_canvas.set("view-box", attr_viewbox)

    def get_width(self):
        return float(self.root_canvas.get("width", "0"))

    def set_width(self, value):
        self.root_canvas.set("width", str(value))
        self._update_viewbox()

    def get_height(self):
        return float(self.root_canvas.get("height", "0"))

    def set_height(self, value):
        self.root_canvas.set("height", str(value))
        self._update_viewbox()

    def get_name(self):
        return self.root_canvas.get("name", "")

    def set_name(self, value):
        self.root_canvas.set("name", value)
        self._update_viewbox()

    width = property(get_width, set_width)
    height = property(get_height, set_height)
    name = property(get_name, set_name)

    # ## Public utility functions

    def new_guid(self):
        """Generate a new GUID"""
        return uuid.uuid4().hex

    # ## Coordinate system conversions

    def distance_svg2sif(self, distance):
        """Convert distance from SVG to Synfig units"""
        return distance / sif.kux

    def distance_sif2svg(self, distance):
        """Convert distance from Synfig to SVG units"""
        return distance * sif.kux

    def coor_svg2sif(self, vector):
        """Convert SVG coordinate [x, y] to Synfig units"""
        x = vector[0]
        y = self.height - vector[1]

        x -= self.width / 2.0
        y -= self.height / 2.0
        x /= sif.kux
        y /= sif.kux

        return [x, y]

    def coor_sif2svg(self, vector):
        """Convert Synfig coordinate [x, y] to SVG units"""
        x = vector[0] * sif.kux + self.width / 2.0
        y = vector[1] * sif.kux + self.height / 2.0

        y = self.height - y

        assert (
            self.coor_svg2sif([x, y]) == vector
        ), "sif to svg coordinate conversion error"

        return [x, y]

    def list_coor_svg2sif(self, l):
        """Scan a list for coordinate pairs and convert them to Synfig units"""
        # If list has two numerical elements,
        # treat it as a coordinate pair
        if type(l) == list and len(l) == 2:
            if type(l[0]) == int or type(l[0]) == float:
                if type(l[1]) == int or type(l[1]) == float:
                    l_sif = self.coor_svg2sif(l)
                    l[0] = l_sif[0]
                    l[1] = l_sif[1]
                    return

        # Otherwise recursively iterate over the list
        for x in l:
            if type(x) == list:
                self.list_coor_svg2sif(x)

    def list_coor_sif2svg(self, l):
        """Scan a list for coordinate pairs and convert them to SVG units"""
        # If list has two numerical elements,
        # treat it as a coordinate pair
        if type(l) == list and len(l) == 2:
            if type(l[0]) == int or type(l[0]) == float:
                if type(l[1]) == int or type(l[1]) == float:
                    l_sif = self.coor_sif2svg(l)
                    l[0] = l_sif[0]
                    l[1] = l_sif[1]
                    return

        # Otherwise recursively iterate over the list
        for x in l:
            if type(x) == list:
                self.list_coor_sif2svg(x)

    def bline_coor_svg2sif(self, b):
        """Convert a BLine from SVG to Synfig coordinate units"""
        self.list_coor_svg2sif(b["points"])

    def bline_coor_sif2svg(self, b):
        """Convert a BLine from Synfig to SVG coordinate units"""
        self.list_coor_sif2svg(b["points"])

    # ## XML Builders -- private
    # ##  used to create XML elements in the Synfig document

    def build_layer(self, layer_type, desc, canvas=None, active=True, version="auto"):
        """Build an empty layer"""
        if canvas is None:
            layer = self.root_canvas.makeelement("layer")
        else:
            layer = etree.SubElement(canvas, "layer")

        layer.set("type", layer_type)
        layer.set("desc", desc)
        if active:
            layer.set("active", "true")
        else:
            layer.set("active", "false")

        if version == "auto":
            version = sif.defaultLayerVersion(layer_type)

        if type(version) == float:
            version = str(version)

        layer.set("version", version)

        return layer

    def _calc_radius(self, p1x, p1y, p2x, p2y):
        """Calculate radius of a tangent given two points"""
        # Synfig tangents are scaled by a factor of 3
        return sif.tangent_scale * math.sqrt((p2x - p1x) ** 2 + (p2y - p1y) ** 2)

    def _calc_angle(self, p1x, p1y, p2x, p2y):
        """Calculate angle (in radians) of a tangent given two points"""
        dx = p2x - p1x
        dy = p2y - p1y
        if dx > 0 and dy > 0:
            ag = math.pi + math.atan(dy / dx)
        elif dx > 0 > dy:
            ag = math.pi + math.atan(dy / dx)
        elif dx < 0 and dy < 0:
            ag = math.atan(dy / dx)
        elif dx < 0 < dy:
            ag = 2 * math.pi + math.atan(dy / dx)
        elif dx == 0 and dy > 0:
            ag = -1 * math.pi / 2
        elif dx == 0 and dy < 0:
            ag = math.pi / 2
        elif dx == 0 and dy == 0:
            ag = 0
        elif dx < 0 and dy == 0:
            ag = 0
        elif dx > 0 and dy == 0:
            ag = math.pi

        return (ag * 180) / math.pi

    def build_param(self, layer, name, value, param_type="auto", guid=None):
        """Add a parameter node to a layer"""
        if layer is None:
            param = self.root_canvas.makeelement("param")
        else:
            param = etree.SubElement(layer, "param")
        param.set("name", name)

        # Automatically detect param_type
        if param_type == "auto":
            if layer is not None:
                layer_type = layer.get("type")
                param_type = sif.paramType(layer_type, name)
            else:
                param_type = sif.paramType(None, name, value)

        if param_type == "real":
            el = etree.SubElement(param, "real")
            el.set("value", str(float(value)))
        elif param_type == "integer":
            el = etree.SubElement(param, "integer")
            el.set("value", str(int(value)))
        elif param_type == "vector":
            el = etree.SubElement(param, "vector")
            x = etree.SubElement(el, "x")
            x.text = str(float(value[0]))
            y = etree.SubElement(el, "y")
            y.text = str(float(value[1]))
        elif param_type == "color":
            el = etree.SubElement(param, "color")
            r = etree.SubElement(el, "r")
            r.text = str(float(value[0]))
            g = etree.SubElement(el, "g")
            g.text = str(float(value[1]))
            b = etree.SubElement(el, "b")
            b.text = str(float(value[2]))
            a = etree.SubElement(el, "a")
            a.text = str(float(value[3])) if len(value) > 3 else "1.0"
        elif param_type == "gradient":
            el = etree.SubElement(param, "gradient")
            # Value is a dictionary of color stops
            #  see get_gradient()
            for pos in value.keys():
                color = etree.SubElement(el, "color")
                color.set("pos", str(float(pos)))

                c = value[pos]

                r = etree.SubElement(color, "r")
                r.text = str(float(c[0]))
                g = etree.SubElement(color, "g")
                g.text = str(float(c[1]))
                b = etree.SubElement(color, "b")
                b.text = str(float(c[2]))
                a = etree.SubElement(color, "a")
                a.text = str(float(c[3])) if len(c) > 3 else "1.0"
        elif param_type == "bool":
            el = etree.SubElement(param, "bool")
            if value:
                el.set("value", "true")
            else:
                el.set("value", "false")
        elif param_type == "time":
            el = etree.SubElement(param, "time")
            if type(value) == int:
                el.set("value", "{:d}s".format(value))
            elif type(value) == float:
                el.set("value", "{:f}s".format(value))
            elif type(value) == str:
                el.set("value", value)
        elif param_type == "bline":
            el = etree.SubElement(param, "bline")
            el.set("type", "bline_point")

            # value is a bline (dictionary type), see path_to_bline_list
            if value["loop"]:
                el.set("loop", "true")
            else:
                el.set("loop", "false")

            for vertex in value["points"]:
                x = float(vertex[1][0])
                y = float(vertex[1][1])

                tg1x = float(vertex[0][0])
                tg1y = float(vertex[0][1])

                tg2x = float(vertex[2][0])
                tg2y = float(vertex[2][1])

                tg1_radius = self._calc_radius(x, y, tg1x, tg1y)
                tg1_angle = self._calc_angle(x, y, tg1x, tg1y)

                tg2_radius = self._calc_radius(x, y, tg2x, tg2y)
                tg2_angle = self._calc_angle(x, y, tg2x, tg2y) - 180.0

                if vertex[3]:
                    split = "true"
                else:
                    split = "false"

                entry = etree.SubElement(el, "entry")
                composite = etree.SubElement(entry, "composite")
                composite.set("type", "bline_point")

                point = etree.SubElement(composite, "point")
                vector = etree.SubElement(point, "vector")
                etree.SubElement(vector, "x").text = str(x)
                etree.SubElement(vector, "y").text = str(y)

                width = etree.SubElement(composite, "width")
                etree.SubElement(width, "real").set("value", "1.0")

                origin = etree.SubElement(composite, "origin")
                etree.SubElement(origin, "real").set("value", "0.5")

                split_el = etree.SubElement(composite, "split")
                etree.SubElement(split_el, "bool").set("value", split)

                t1 = etree.SubElement(composite, "t1")
                t2 = etree.SubElement(composite, "t2")

                t1_rc = etree.SubElement(t1, "radial_composite")
                t1_rc.set("type", "vector")

                t2_rc = etree.SubElement(t2, "radial_composite")
                t2_rc.set("type", "vector")

                t1_r = etree.SubElement(t1_rc, "radius")
                t2_r = etree.SubElement(t2_rc, "radius")
                t1_radius = etree.SubElement(t1_r, "real")
                t2_radius = etree.SubElement(t2_r, "real")
                t1_radius.set("value", str(tg1_radius))
                t2_radius.set("value", str(tg2_radius))

                t1_t = etree.SubElement(t1_rc, "theta")
                t2_t = etree.SubElement(t2_rc, "theta")
                t1_angle = etree.SubElement(t1_t, "angle")
                t2_angle = etree.SubElement(t2_t, "angle")
                t1_angle.set("value", str(tg1_angle))
                t2_angle.set("value", str(tg2_angle))
        elif param_type == "canvas":
            el = etree.SubElement(param, "canvas")
            el.set("xres", "10.0")
            el.set("yres", "10.0")

            # "value" is a list of layers
            if value is not None:
                for layer in value:
                    el.append(layer)
        else:
            raise AssertionError("Unsupported param type {}".format(param_type))

        if guid:
            el.set("guid", guid)
        else:
            el.set("guid", self.new_guid())

        return param

    # ## Public layer API
    # ##  Should be used by outside functions to create layers and set layer parameters

    def create_layer(
        self,
        layer_type,
        desc,
        params={},
        guids={},
        canvas=None,
        active=True,
        version="auto",
    ):
        """Create a new layer

        Keyword arguments:
        layer_type -- layer type string used internally by Synfig
        desc -- layer description
        params -- a dictionary of parameter names and their values
        guids -- a dictionary of parameter types and their guids (optional)
        active -- set to False to create a hidden layer
        """
        layer = self.build_layer(layer_type, desc, canvas, active, version)
        default_layer_params = sif.defaultLayerParams(layer_type)

        for param_name in default_layer_params.keys():
            param_type = default_layer_params[param_name][0]
            if param_name in params.keys():
                param_value = params[param_name]
            else:
                param_value = default_layer_params[param_name][1]

            if param_name in guids.keys():
                param_guid = guids[param_name]
            else:
                param_guid = None

            if param_value is not None:
                self.build_param(
                    layer, param_name, param_value, param_type, guid=param_guid
                )

        return layer

    def set_param(
        self, layer, name, value, param_type="auto", guid=None, modify_linked=False
    ):
        """Set a layer parameter

        Keyword arguments:
        layer -- the layer to set the parameter for
        name -- parameter name
        value -- parameter value
        param_type -- parameter type (default "auto")
        guid -- guid of the parameter value
        """
        if modify_linked:
            raise AssertionError("Modifying linked parameters is not supported")

        layer_type = layer.get("type")
        assert layer_type, "Layer does not have a type"

        if param_type == "auto":
            param_type = sif.paramType(layer_type, name)

        # Remove existing parameters with this name
        existing = []
        for param in layer.iterchildren():
            if param.get("name") == name:
                existing.append(param)

        if len(existing) == 0:
            self.build_param(layer, name, value, param_type, guid)
        elif len(existing) > 1:
            raise AssertionError("Found multiple parameters with the same name")
        else:
            new_param = self.build_param(None, name, value, param_type, guid)
            layer.replace(existing[0], new_param)

    def set_params(self, layer, params={}, guids={}, modify_linked=False):
        """Set layer parameters

        Keyword arguments:
        layer -- the layer to set the parameter for
        params -- a dictionary of parameter names and their values
        guids -- a dictionary of parameter types and their guids (optional)
        """
        for param_name in params.keys():
            if param_name in guids.keys():
                self.set_param(
                    layer,
                    param_name,
                    params[param_name],
                    guid=guids[param_name],
                    modify_linked=modify_linked,
                )
            else:
                self.set_param(
                    layer, param_name, params[param_name], modify_linked=modify_linked
                )

    def get_param(self, layer, name, param_type="auto"):
        """Get the value of a layer parameter

        Keyword arguments:
        layer -- the layer to get the parameter from
        name -- param name
        param_type -- parameter type (default "auto")

        NOT FULLY IMPLEMENTED
        """
        layer_type = layer.get("type")
        assert layer_type, "Layer does not have a type"

        if param_type == "auto":
            param_type = sif.paramType(layer_type, name)

        for param in layer.iterchildren():
            if param.get("name") == name:
                if param_type == "real":
                    return float(param[0].get("value", "0"))
                elif param_type == "integer":
                    return int(param[0].get("integer", "0"))
                else:
                    raise Exception(
                        "Getting this type of parameter not yet implemented"
                    )

    # ## Global defs, and related

    # SVG Filters
    def add_filter(self, filter_id, f):
        """Register a filter"""
        self.filters[filter_id] = f

    # SVG Gradients
    def add_linear_gradient(
        self,
        gradient_id,
        p1,
        p2,
        mtx=[[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]],
        stops=[],
        link="",
        spread_method="pad",
    ):
        """Register a linear gradient definition"""
        gradient = {
            "type": "linear",
            "p1": p1,
            "p2": p2,
            "mtx": mtx,
            "spreadMethod": spread_method,
        }
        if stops:
            gradient["stops"] = stops
            gradient["stops_guid"] = self.new_guid()
        elif link != "":
            gradient["link"] = link
        else:
            raise MalformedSVGError("Gradient has neither stops nor link")
        self.gradients[gradient_id] = gradient

    def add_radial_gradient(
        self,
        gradient_id,
        center,
        radius,
        focus,
        mtx=[[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]],
        stops=[],
        link="",
        spread_method="pad",
    ):
        """Register a radial gradient definition"""
        gradient = {
            "type": "radial",
            "center": center,
            "radius": radius,
            "focus": focus,
            "mtx": mtx,
            "spreadMethod": spread_method,
        }
        if stops:
            gradient["stops"] = stops
            gradient["stops_guid"] = self.new_guid()
        elif link != "":
            gradient["link"] = link
        else:
            raise MalformedSVGError("Gradient has neither stops nor link")
        self.gradients[gradient_id] = gradient

    def get_gradient(self, gradient_id):
        """
        Return a gradient with a given id

        Linear gradient format:
        {
        "type"      : "linear",
        "p1"        : [x, y],
        "p2"        : [x, y],
        "mtx"       : mtx,
        "stops"     : color stops,
        "stops_guid": color stops guid,
        "spreadMethod": "pad", "reflect", or "repeat"
        }

        Radial gradient format:
        {
        "type"      : "radial",
        "center"    : [x, y],
        "radius"    : r,
        "focus"     : [x, y],
        "mtx"       : mtx,
        "stops"     : color stops,
        "stops_guid": color stops guid,
        "spreadMethod": "pad", "reflect", or "repeat"
        }

        Color stops format
        {
        0.0         : color ([r,g,b,a] or [r,g,b]) at start,
        [a number]  : color at that position,
        1.0         : color at end
        }
        """

        if gradient_id not in self.gradients.keys():
            return None

        gradient = self.gradients[gradient_id]

        # If the gradient has no link, we are done
        if "link" not in gradient.keys() or gradient["link"] == "":
            return gradient

        # If the gradient does have a link, find the color stops recursively
        if gradient["link"] not in self.gradients.keys():
            raise MalformedSVGError("Linked gradient ID not found")

        linked_gradient = self.get_gradient(gradient["link"])
        gradient["stops"] = linked_gradient["stops"]
        gradient["stops_guid"] = linked_gradient["stops_guid"]
        del gradient["link"]

        # Update the gradient in our listing
        # (so recursive lookup only happens once)
        self.gradients[gradient_id] = gradient

        return gradient

    def gradient_to_params(self, gradient):
        """Transform gradient to a list of parameters to pass to a Synfig layer"""
        # Create a copy of the gradient
        g = gradient.copy()

        # Set synfig-only attribs
        if g["spreadMethod"] == "repeat":
            g["loop"] = True
        elif g["spreadMethod"] == "reflect":
            g["loop"] = True
            # Reflect the gradient
            # Original: 0.0 [A . B . C] 1.0
            # New:      0.0 [A . B . C . B . A] 1.0
            #           (with gradient size doubled)
            new_stops = {}

            # reflect the stops
            for pos in g["stops"]:
                val = g["stops"][pos]
                if pos == 1.0:
                    new_stops[pos / 2.0] = val
                else:
                    new_stops[pos / 2.0] = val
                    new_stops[1 - pos / 2.0] = val
            g["stops"] = new_stops

            # double the gradient size
            if g["type"] == "linear":
                g["p2"] = [
                    g["p1"][0] + 2.0 * (g["p2"][0] - g["p1"][0]),
                    g["p1"][1] + 2.0 * (g["p2"][1] - g["p1"][1]),
                ]
            if g["type"] == "radial":
                g["radius"] *= 2.0

        # Rename "stops" to "gradient"
        g["gradient"] = g["stops"]

        # Convert coordinates
        if g["type"] == "linear":
            g["p1"] = self.coor_svg2sif(g["p1"])
            g["p2"] = self.coor_svg2sif(g["p2"])

        if g["type"] == "radial":
            g["center"] = self.coor_svg2sif(g["center"])
            g["radius"] = self.distance_svg2sif(g["radius"])

        # Delete extra attribs
        removed_attribs = [
            "type",
            "stops",
            "stops_guid",
            "mtx",
            "focus",
            "spreadMethod",
        ]
        for x in removed_attribs:
            if x in g.keys():
                del g[x]
        return g

    # ## Public operations API
    # Operations act on a series of layers, and (optionally) on a series of named parameters
    # The "is_end" attribute should be set to true when the layers are at the end of a canvas
    # (i.e. when adding transform layers on top of them does not require encapsulation)

    def op_blur(self, layers, x, y, name="Blur", is_end=False):
        """Gaussian blur the given layers by the given x and y amounts

        Keyword arguments:
        layers -- list of layers
        x -- x-amount of blur
        y -- x-amount of blur
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        blur = self.create_layer(
            "blur",
            name,
            params={"blend_method": sif.blend_methods["straight"], "size": [x, y]},
        )

        if is_end:
            return layers + [blur]
        else:
            return self.op_encapsulate(layers + [blur])

    def op_color(self, layers, overlay, is_end=False):
        """Apply a color overlay to the given layers

        Should be used to apply a gradient or pattern to a shape

        Keyword arguments:
        layers -- list of layers
        overlay -- color layer to apply
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        if not layers:
            return layers
        if overlay is None:
            return layers

        overlay_enc = self.op_encapsulate([overlay])
        self.set_param(
            overlay_enc[0], "blend_method", sif.blend_methods["straight onto"]
        )
        ret = layers + overlay_enc

        if is_end:
            return ret
        else:
            return self.op_encapsulate(ret)

    def op_encapsulate(self, layers, name="Inline Canvas", is_end=False):
        """Encapsulate the given layers

        Keyword arguments:
        layers -- list of layers
        name -- Name of the PasteCanvas layer that is created
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of one layer
        """

        if not layers:
            return layers

        layer = self.create_layer("PasteCanvas", name, params={"canvas": layers})
        return [layer]

    def op_fade(self, layers, opacity, is_end=False):
        """Increase the opacity of the given layers by a certain amount

        Keyword arguments:
        layers -- list of layers
        opacity -- the opacity to apply (float between 0.0 to 1.0)
        name -- name of the Transform layer that is added
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        # If there is blending involved, first encapsulate the layers
        for layer in layers:
            if self.get_param(layer, "blend_method") != sif.blend_methods["composite"]:
                return self.op_fade(self.op_encapsulate(layers), opacity, is_end)

        # Otherwise, set their amount
        for layer in layers:
            amount = self.get_param(layer, "amount")
            self.set_param(layer, "amount", amount * opacity)

        return layers

    def op_filter(self, layers, filter_id, is_end=False):
        """Apply a filter to the given layers

        Keyword arguments:
        layers -- list of layers
        filter_id -- id of the filter
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        if filter_id not in self.filters.keys():
            raise MalformedSVGError("Filter {} not found".format(filter_id))

        try:
            ret = self.filters[filter_id](self, layers, is_end)
            assert type(ret) == list
            return ret
        except UnsupportedException:
            # If the filter is not supported, ignore it.
            return layers

    def op_set_blend(self, layers, blend_method, is_end=False):
        """Set the blend method of the given group of layers

        If more than one layer is supplied, they will be encapsulated.

        Keyword arguments:
        layers -- list of layers
        blend_method -- blend method to give the layers
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        if not layers:
            return layers
        if blend_method == "composite":
            return layers

        layer = layers[0]
        if len(layers) > 1 or self.get_param(layers[0], "amount") != 1.0:
            layer = self.op_encapsulate(layers)[0]

        layer = deepcopy(layer)

        self.set_param(layer, "blend_method", sif.blend_methods[blend_method])

        return [layer]

    def op_transform(self, layers, mtx, name="Transform", is_end=False):
        """Apply a matrix transformation to the given layers

        Keyword arguments:
        layers -- list of layers
        mtx -- transformation matrix
        name -- name of the Transform layer that is added
        is_end -- set to True if layers are at the end of a canvas

        Returns: list of layers
        """
        if not layers:
            return layers
        if mtx is None or mtx == [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]:
            return layers

        src_tl = [100, 100]
        src_br = [200, 200]

        dest_tl = [100, 100]
        dest_tr = [200, 100]
        dest_br = [200, 200]
        dest_bl = [100, 200]

        dest_tl = Transform(mtx).apply_to_point(dest_tl)
        dest_tr = Transform(mtx).apply_to_point(dest_tr)
        dest_br = Transform(mtx).apply_to_point(dest_br)
        dest_bl = Transform(mtx).apply_to_point(dest_bl)

        warp = self.create_layer(
            "warp",
            name,
            params={
                "src_tl": self.coor_svg2sif(src_tl),
                "src_br": self.coor_svg2sif(src_br),
                "dest_tl": self.coor_svg2sif(dest_tl),
                "dest_tr": self.coor_svg2sif(dest_tr),
                "dest_br": self.coor_svg2sif(dest_br),
                "dest_bl": self.coor_svg2sif(dest_bl),
            },
        )

        if is_end:
            return layers + [warp]
        else:
            return self.op_encapsulate(layers + [warp])


# ##### Utility Functions ##################################

# ## Path related


def path_to_bline_list(path_d, nodetypes=None, mtx=[[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]):
    """
    Convert a path to a BLine List

    bline_list format:

    Vertex:
    [[tg1x, tg1y], [x,y], [tg2x, tg2y], split = T/F]
    Vertex list:
    [ vertex, vertex, vertex, ...]
    Bline:
    {
    "points"    : vertex_list,
    "loop"      : True / False
    }
    """

    # Exit on empty paths
    if not path_d:
        return []

    # Parse the path
    path = Path(path_d).to_arrays()

    # Append (more than) enough c's to the nodetypes
    if nodetypes is None:
        nt = ""
    else:
        nt = nodetypes

    for _ in range(len(path)):
        nt += "c"

    # Create bline list
    #     borrows code from cubicsuperpath.py

    # bline_list := [bline, bline, ...]
    # bline := {
    #           "points":[vertex, vertex, ...],
    #           "loop":True/False,
    #          }

    bline_list = []

    subpathstart = []
    last = []
    lastctrl = []
    lastsplit = True

    for s in path:
        cmd, params = s
        if cmd != "M" and bline_list == []:
            raise MalformedSVGError(
                "Bad path data: path doesn't start with moveto, {}, {}".format(s, path)
            )
        elif cmd == "M":
            # Add previous point to subpath
            if last:
                bline_list[-1]["points"].append(
                    [lastctrl[:], last[:], last[:], lastsplit]
                )
            # Start a new subpath
            bline_list.append({"nodetypes": "", "loop": False, "points": []})
            # Save coordinates of this point
            subpathstart = params[:]
            last = params[:]
            lastctrl = params[:]
            lastsplit = False if nt[0] == "z" else True
            nt = nt[1:]
        elif cmd in "LHV":
            bline_list[-1]["points"].append([lastctrl[:], last[:], last[:], lastsplit])
            if cmd == "H":
                last = [params[0], last[1]]
                lastctrl = [params[0], last[1]]
            elif cmd == "V":
                last = [last[0], params[0]]
                lastctrl = [last[0], params[0]]
            else:
                last = params[:]
                lastctrl = params[:]
            lastsplit = False if nt[0] == "z" else True
            nt = nt[1:]
        elif cmd == "C":
            bline_list[-1]["points"].append(
                [lastctrl[:], last[:], params[:2], lastsplit]
            )
            last = params[-2:]
            lastctrl = params[2:4]
            lastsplit = False if nt[0] == "z" else True
            nt = nt[1:]
        elif cmd == "Q":
            q0 = last[:]
            q1 = params[0:2]
            q2 = params[2:4]
            x0 = q0[0]
            x1 = 1.0 / 3 * q0[0] + 2.0 / 3 * q1[0]
            x2 = 2.0 / 3 * q1[0] + 1.0 / 3 * q2[0]
            x3 = q2[0]
            y0 = q0[1]
            y1 = 1.0 / 3 * q0[1] + 2.0 / 3 * q1[1]
            y2 = 2.0 / 3 * q1[1] + 1.0 / 3 * q2[1]
            y3 = q2[1]
            bline_list[-1]["points"].append(
                [lastctrl[:], [x0, y0], [x1, y1], lastsplit]
            )
            last = [x3, y3]
            lastctrl = [x2, y2]
            lastsplit = False if nt[0] == "z" else True
            nt = nt[1:]
        elif cmd == "A":
            from inkex.paths import arc_to_path

            arcp = arc_to_path(last[:], params[:])
            arcp[0][0] = lastctrl[:]
            last = arcp[-1][1]
            lastctrl = arcp[-1][0]
            lastsplit = False if nt[0] == "z" else True
            nt = nt[1:]
            for el in arcp[:-1]:
                el.append(True)
                bline_list[-1]["points"].append(el)
        elif cmd == "Z":
            if len(bline_list[-1]["points"]) == 0:
                # If the path "loops" after only one point
                #  e.g. "M 0 0 Z"
                bline_list[-1]["points"].append([lastctrl[:], last[:], last[:], False])
            elif last == subpathstart:
                # If we are back to the original position
                # merge our tangent into the first point
                bline_list[-1]["points"][0][0] = lastctrl[:]
            else:
                # Otherwise draw a line to the starting point
                bline_list[-1]["points"].append(
                    [lastctrl[:], last[:], last[:], lastsplit]
                )

            # Clear the variables (no more points need to be added)
            last = []
            lastctrl = []
            lastsplit = True

            # Loop the subpath
            bline_list[-1]["loop"] = True
    # Append final superpoint, if needed
    if last:
        bline_list[-1]["points"].append([lastctrl[:], last[:], last[:], lastsplit])

    # Apply the transformation
    if mtx != [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0]]:
        for bline in bline_list:
            for vertex in bline["points"]:
                for point in vertex:
                    if not isinstance(point, bool):
                        pnt = Transform(mtx).apply_to_point(point)
                        point[0], point[1] = pnt[0], pnt[1]

    return bline_list


# ## Style related


def extract_color(style, color_attrib, *opacity_attribs):
    if color_attrib in style.keys():
        if style[color_attrib] == "none":
            return [1, 1, 1, 0]
        c = style(color_attrib).to_rgb()
    else:
        c = (0, 0, 0)

    # Convert color scales and adjust gamma
    color = [
        pow(c[0] / 255.0, sif.gamma),
        pow(c[1] / 255.0, sif.gamma),
        pow(c[2] / 255.0, sif.gamma),
        1.0,
    ]

    for opacity in opacity_attribs:
        if opacity in style.keys():
            color[3] *= float(style[opacity])
    return color


def extract_opacity(style, *opacity_attribs):
    ret = 1.0
    for opacity in opacity_attribs:
        if opacity in style.keys():
            ret *= float(style[opacity])
    return ret


def extract_width(style, width_attrib, mtx):
    if width_attrib in style.keys():
        width = get_dimension(style[width_attrib])
    else:
        width = 1

    area_scale_factor = mtx[0][0] * mtx[1][1] - mtx[0][1] * mtx[1][0]
    linear_scale_factor = math.sqrt(abs(area_scale_factor))

    return width * linear_scale_factor / sif.kux


# ##### Main Class #########################################
class SynfigExport(OutputExtension):
    def preprocess(self):
        """Transform document in preparation for exporting it into the Synfig format"""

        # Convert objects to path
        super().preprocess()

        # Remove inheritance of attributes
        propagate_attribs(self.document.getroot())

        # Fuse multiple subpaths in fills
        for node in self.document.getroot().xpath("//svg:path"):
            if node.get("d", "").lower().count("m") > 1:
                # There are multiple subpaths
                fill = split_fill_and_stroke(node)[0]
                if fill is not None:
                    fill.path = fuse_subpaths(fill.path)

    def effect(self):
        # Prepare the document for exporting
        self.preprocess()
        svg = self.document.getroot()
        width = get_dimension(svg.get("width", 1024))
        height = get_dimension(svg.get("height", 768))

        title = svg.getElement("svg:title")
        if title is not None:
            name = title.text
        else:
            name = svg.get("sodipodi:docname", "Synfig Animation 1")

        doc = SynfigDocument(width, height, name)

        layers = []
        for node in svg.iterchildren():
            layers += self.convert_node(node, doc)

        root_canvas = doc.get_root_canvas()
        for layer in layers:
            root_canvas.append(layer)

        self.synfig_document = doc.get_root_tree()

    def save(self, stream):
        self.synfig_document.write(stream)

    def convert_node(self, node, d):
        """Convert an SVG node to a list of Synfig layers"""
        # Parse tags that don't draw any layers
        if isinstance(node, SvgDocumentElement):
            self.parse_defs(node, d)
            return []
        elif not isinstance(
            node, (Group, Anchor, Switch, PathElement, Metadata, NamedView)
        ):
            # An unsupported element
            return []

        layers = []
        if isinstance(node, Group):
            for subnode in node:
                layers += self.convert_node(subnode, d)
            if isinstance(node, Layer):
                name = node.label or "Inline Canvas"
                layers = d.op_encapsulate(layers, name=name)

        elif isinstance(node, (Anchor, Switch)):
            # Treat anchor and switch as a group
            for subnode in node:
                layers += self.convert_node(subnode, d)
        elif isinstance(node, PathElement):
            layers = self.convert_path(node, d)

        style = node.style
        if "filter" in style.keys() and style["filter"].startswith("url"):
            filter_id = style["filter"][5:].split(")")[0]
            layers = d.op_filter(layers, filter_id)

        opacity = extract_opacity(style, "opacity")
        if opacity != 1.0:
            layers = d.op_fade(layers, opacity)

        return layers

    def parse_defs(self, node, d):
        for child in node.iterchildren():
            if isinstance(child, Gradient):
                self.parse_gradient(child, d)
            elif child.TAG == "filter":
                self.parse_filter(child, d)

    def parse_gradient(self, node, d):
        if node.TAG == "linearGradient":
            gradient_id = node.get("id", str(id(node)))
            x1 = float(node.get("x1", "0.0"))
            x2 = float(node.get("x2", "0.0"))
            y1 = float(node.get("y1", "0.0"))
            y2 = float(node.get("y2", "0.0"))

            mtx = node.gradientTransform.matrix

            link = node.get("xlink:href", "#")[1:]
            spread_method = node.get("spreadMethod", "pad")
            if link == "":
                stops = self.parse_stops(node, d)
                d.add_linear_gradient(
                    gradient_id,
                    [x1, y1],
                    [x2, y2],
                    mtx,
                    stops=stops,
                    spread_method=spread_method,
                )
            else:
                d.add_linear_gradient(
                    gradient_id,
                    [x1, y1],
                    [x2, y2],
                    mtx,
                    link=link,
                    spread_method=spread_method,
                )
        elif node.TAG == "radialGradient":
            gradient_id = node.get("id", str(id(node)))
            cx = float(node.get("cx", "0.0"))
            cy = float(node.get("cy", "0.0"))
            r = float(node.get("r", "0.0"))
            fx = float(node.get("fx", "0.0"))
            fy = float(node.get("fy", "0.0"))

            mtx = node.gradientTransform.matrix

            link = node.get("xlink:href", "#")[1:]
            spread_method = node.get("spreadMethod", "pad")
            if link == "":
                stops = self.parse_stops(node, d)
                d.add_radial_gradient(
                    gradient_id,
                    [cx, cy],
                    r,
                    [fx, fy],
                    mtx,
                    stops=stops,
                    spread_method=spread_method,
                )
            else:
                d.add_radial_gradient(
                    gradient_id,
                    [cx, cy],
                    r,
                    [fx, fy],
                    mtx,
                    link=link,
                    spread_method=spread_method,
                )

    def parse_stops(self, node, d):
        stops = {}
        for stop in node.iterchildren():
            if stop.TAG == "stop":
                offset = float(stop.get("offset"))
                style = stop.style
                stops[offset] = extract_color(style, "stop-color", "stop-opacity")
            else:
                raise MalformedSVGError("Child of gradient is not a stop")

        return stops

    def parse_filter(self, node, d):
        filter_id = node.get("id", str(id(node)))

        # A filter is just like an operator (the op_* functions),
        # except that it's created here
        def the_filter(d, layers, is_end=False):
            refs = {None: layers, "SourceGraphic": layers}  # default
            encapsulate_result = not is_end

            for child in node.iterchildren():
                if child.get("in") not in refs:
                    # "SourceAlpha", "BackgroundImage",
                    # "BackgroundAlpha", "FillPaint", "StrokePaint"
                    # are not supported
                    raise UnsupportedException
                l_in = refs[child.get("in")]
                l_out = []
                if child.TAG == "feGaussianBlur":
                    std_dev = child.get("stdDeviation", "0")
                    std_dev = std_dev.replace(",", " ").split()
                    x = float(std_dev[0])
                    if len(std_dev) > 1:
                        y = float(std_dev[1])
                    else:
                        y = x

                    if x == 0 and y == 0:
                        l_out = l_in
                    else:
                        x = d.distance_svg2sif(x)
                        y = d.distance_svg2sif(y)
                        l_out = d.op_blur(l_in, x, y, is_end=True)
                elif child.TAG == "feBlend":
                    # Note: Blend methods are not an exact match
                    # because SVG uses alpha channel in places where
                    # Synfig does not
                    mode = child.get("mode", "normal")
                    if mode == "normal":
                        blend_method = "composite"
                    elif mode == "multiply":
                        blend_method = "multiply"
                    elif mode == "screen":
                        blend_method = "screen"
                    elif mode == "darken":
                        blend_method = "darken"
                    elif mode == "lighten":
                        blend_method = "brighten"
                    else:
                        raise MalformedSVGError("Invalid blend method")

                    if child.get("in2") == "BackgroundImage":
                        encapsulate_result = False
                        l_out = d.op_set_blend(l_in, blend_method) + d.op_set_blend(
                            l_in, "behind"
                        )
                    elif child.get("in2") not in refs:
                        raise UnsupportedException
                    else:
                        l_in2 = refs[child.get("in2")]
                        l_out = l_in2 + d.op_set_blend(l_in, blend_method)

                else:
                    # This filter element is currently unsupported
                    raise UnsupportedException

                # Output the layers
                if child.get("result"):
                    refs[child.get("result")] = l_out

                # Set the default for the next filter element
                refs[None] = l_out

            # Return the output from the last element
            if len(refs[None]) > 1 and encapsulate_result:
                return d.op_encapsulate(refs[None])
            else:
                return refs[None]

        d.add_filter(filter_id, the_filter)

    def convert_path(self, node, d):
        """Convert an SVG path node to a list of Synfig layers"""
        layers = []

        node_id = node.get("id", str(id(node)))
        style = node.style

        mtx = node.transform.matrix
        blines = path_to_bline_list(node.get("d"), node.get("sodipodi:nodetypes"), mtx)
        for bline in blines:
            d.bline_coor_svg2sif(bline)
            bline_guid = d.new_guid()

            if style.setdefault("fill", "#000000") != "none":
                if style["fill"].startswith("url"):
                    # Set the color to black, so we can later overlay
                    # the shape with a gradient or pattern
                    color = [0, 0, 0, 1]
                else:
                    color = extract_color(style, "fill", "fill-opacity")

                layer = d.create_layer(
                    "region",
                    node_id,
                    {
                        "bline": bline,
                        "color": color,
                        "winding_style": 1
                        if style.setdefault("fill-rule", "nonzero") == "evenodd"
                        else 0,
                    },
                    guids={"bline": bline_guid},
                )

                if style["fill"].startswith("url"):
                    color_layer = self.convert_url(
                        style["fill"][5:].split(")")[0], mtx, d
                    )[0]
                    layer = d.op_color([layer], overlay=color_layer)[0]
                    layer = d.op_fade([layer], extract_opacity(style, "fill-opacity"))[
                        0
                    ]

                layers.append(layer)

            if style.setdefault("stroke", "none") != "none":
                if style["stroke"].startswith("url"):
                    # Set the color to black, so we can later overlay
                    # the shape with a gradient or pattern
                    color = [0, 0, 0, 1]
                else:
                    color = extract_color(style, "stroke", "stroke-opacity")

                layer = d.create_layer(
                    "outline",
                    node_id,
                    {
                        "bline": bline,
                        "color": color,
                        "width": extract_width(style, "stroke-width", mtx),
                        "sharp_cusps": True
                        if style.setdefault("stroke-linejoin", "miter") == "miter"
                        else False,
                        "round_tip[0]": False
                        if style.setdefault("stroke-linecap", "butt") == "butt"
                        else True,
                        "round_tip[1]": False
                        if style.setdefault("stroke-linecap", "butt") == "butt"
                        else True,
                    },
                    guids={"bline": bline_guid},
                )

                if style["stroke"].startswith("url"):
                    color_layer = self.convert_url(
                        style["stroke"][5:].split(")")[0], mtx, d
                    )[0]
                    layer = d.op_color([layer], overlay=color_layer)[0]
                    layer = d.op_fade(
                        [layer], extract_opacity(style, "stroke-opacity")
                    )[0]

                layers.append(layer)

        return layers

    def convert_url(self, url_id, mtx, d):
        """Return a list Synfig layers that represent the gradient with the given id"""
        gradient = d.get_gradient(url_id)
        if gradient is None:
            # Patterns and other URLs not supported
            return [None]

        if gradient["type"] == "linear":
            layer = d.create_layer(
                "linear_gradient",
                url_id,
                d.gradient_to_params(gradient),
                guids={"gradient": gradient["stops_guid"]},
            )

        if gradient["type"] == "radial":
            layer = d.create_layer(
                "radial_gradient",
                url_id,
                d.gradient_to_params(gradient),
                guids={"gradient": gradient["stops_guid"]},
            )

        trm = Transform(mtx) * Transform(gradient["mtx"])
        return d.op_transform([layer], trm.matrix)


if __name__ == "__main__":
    SynfigExport().run()
