#
# Copyright (C) 2016-2019 by Nathan Lovato, Daniel Oakey, Razvan Radulescu, and contributors
#
# This file is part of Power Sequencer.
#
# Power Sequencer 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 3 of the
# License, or (at your option) any later version.
#
# Power Sequencer 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 Power Sequencer. If
# not, see <https://www.gnu.org/licenses/>.
#
import bpy
from mathutils import Vector
from math import floor

from .utils.doc import doc_name, doc_idname, doc_brief, doc_description


class POWER_SEQUENCER_OT_fade_add(bpy.types.Operator):
    """*brief* Adds or updates a fade animation for either visual or audio strips.

    Fade options:

    - In, Out, In and Out create a fade animation of the given duration from
    the start of the sequence, to the end of the sequence, or on both sides
    - From playhead: the fade animation goes from the start of sequences under the playhead to the playhead
    - To playhead: the fade animation goes from the playhead to the end of sequences under the playhead

    By default, the duration of the fade is 1 second.
    """

    doc = {
        "name": doc_name(__qualname__),
        "demo": "https://i.imgur.com/XoUM2vw.gif",
        "description": doc_description(__doc__),
        "shortcuts": [
            ({"type": "F", "value": "PRESS", "alt": True}, {"type": "OUT"}, "Fade Out"),
            ({"type": "F", "value": "PRESS", "ctrl": True}, {"type": "IN"}, "Fade In"),
            ({"type": "F", "value": "PRESS"}, {"type": "IN_OUT"}, "Fade In and Out"),
        ],
        "keymap": "Sequencer",
    }
    bl_idname = doc_idname(__qualname__)
    bl_label = doc["name"]
    bl_description = doc_brief(doc["description"])
    bl_options = {"REGISTER", "UNDO"}

    duration_seconds: bpy.props.FloatProperty(
        name="Fade Duration", description="Duration of the fade in seconds", default=1.0, min=0.01
    )
    type: bpy.props.EnumProperty(
        items=[
            ("IN_OUT", "Fade in and out", "Fade selected strips in and out"),
            ("IN", "Fade in", "Fade in selected strips"),
            ("OUT", "Fade out", "Fade out selected strips"),
            (
                "CURSOR_FROM",
                "From playhead",
                "Fade from the time cursor to the end of overlapping sequences",
            ),
            (
                "CURSOR_TO",
                "To playhead",
                "Fade from the start of sequences under the time cursor to the current frame",
            ),
        ],
        name="Fade type",
        description="Fade in, out, or both in and out. Default is both",
        default="IN_OUT",
    )

    @classmethod
    def poll(cls, context):
        return context.selected_sequences

    def execute(self, context):
        # We must create a scene action first if there's none
        scene = context.scene
        if not scene.animation_data:
            scene.animation_data_create()
        if not scene.animation_data.action:
            action = bpy.data.actions.new(scene.name + "Action")
            scene.animation_data.action = action

        sequences = context.selected_sequences
        if self.type in ["CURSOR_TO", "CURSOR_FROM"]:
            sequences = [
                s
                for s in sequences
                if s.frame_final_start < context.scene.frame_current < s.frame_final_end
            ]

        max_duration = min(sequences, key=lambda s: s.frame_final_duration).frame_final_duration
        max_duration = floor(max_duration / 2.0) if self.type == "IN_OUT" else max_duration

        faded_sequences = []
        for sequence in sequences:
            duration = self.calculate_fade_duration(context, sequence)
            duration = min(duration, max_duration)

            if not self.is_long_enough(sequence, duration):
                continue

            animated_property = "volume" if hasattr(sequence, "volume") else "blend_alpha"
            fade_fcurve = fade_find_or_create_fcurve(context, sequence, animated_property)
            fades = self.calculate_fades(sequence, fade_fcurve, animated_property, duration)
            fade_animation_clear(context, fade_fcurve, fades)
            fade_animation_create(fade_fcurve, fades)
            faded_sequences.append(sequence)

        sequence_string = "sequence" if len(faded_sequences) == 1 else "sequences"
        self.report(
            {"INFO"}, "Added fade animation to {} {}.".format(len(faded_sequences), sequence_string)
        )
        return {"FINISHED"}

    def calculate_fade_duration(self, context, sequence):
        frame_current = context.scene.frame_current
        duration = 0.0
        if self.type == "CURSOR_TO":
            duration = abs(frame_current - sequence.frame_final_start)
        elif self.type == "CURSOR_FROM":
            duration = abs(sequence.frame_final_end - frame_current)
        else:
            duration = calculate_duration_frames(context, self.duration_seconds)
        return max(1, duration)

    def is_long_enough(self, sequence, duration=0.0):
        minimum_duration = duration * 2 if self.type == "IN_OUT" else duration
        return sequence.frame_final_duration >= minimum_duration

    def calculate_fades(self, sequence, fade_fcurve, animated_property, duration):
        """
        Returns a list of Fade objects
        """
        fades = []
        if self.type in ["IN", "IN_OUT", "CURSOR_TO"]:
            fade = Fade(sequence, fade_fcurve, "IN", animated_property, duration)
            fades.append(fade)
        if self.type in ["OUT", "IN_OUT", "CURSOR_FROM"]:
            fade = Fade(sequence, fade_fcurve, "OUT", animated_property, duration)
            fades.append(fade)
        return fades


def fade_find_or_create_fcurve(context, sequence, animated_property):
    """
    Iterates over all the fcurves until it finds an fcurve with a data path
    that corresponds to the sequence.
    Returns the matching FCurve or creates a new one if the function can't find a match.
    """
    fade_fcurve = None
    fcurves = context.scene.animation_data.action.fcurves
    searched_data_path = sequence.path_from_id(animated_property)
    for fcurve in fcurves:
        if fcurve.data_path == searched_data_path:
            fade_fcurve = fcurve
            break
    if not fade_fcurve:
        fade_fcurve = fcurves.new(data_path=searched_data_path)
    return fade_fcurve


def fade_animation_clear(context, fade_fcurve, fades):
    """
    Removes existing keyframes in the fades' time range, in fast mode, without
    updating the fcurve
    """
    keyframe_points = fade_fcurve.keyframe_points
    for keyframe in keyframe_points:
        for fade in fades:
            # The keyframe points list doesn't seem to always update as the
            # operator re-runs Leading to trying to remove nonexistent keyframes
            try:
                if fade.start.x < keyframe.co[0] < fade.end.x:
                    keyframe_points.remove(keyframe, fast=True)
            except ReferenceError:
                pass


def fade_animation_create(fade_fcurve, fades):
    """
    Inserts keyframes in the fade_fcurve in fast mode using the Fade objects.
    Updates the fcurve after having inserted all keyframes to finish the animation.
    """
    keyframe_points = fade_fcurve.keyframe_points
    for fade in fades:
        for point in (fade.start, fade.end):
            keyframe_points.insert(frame=point.x, value=point.y, options={"FAST"})
    fade_fcurve.update()
    # The graph editor and the audio waveforms only redraw upon "moving" a keyframe
    keyframe_points[-1].co = keyframe_points[-1].co


class Fade:
    """
    Data structure to represent fades
    """

    type = ""
    animated_property = ""
    duration = -1
    max_value = 1.0
    start, end = Vector((0, 0)), Vector((0, 0))

    def __init__(self, sequence, fade_fcurve, type, animated_property, duration):
        self.type = type
        self.animated_property = animated_property
        self.duration = duration
        self.max_value = self.calculate_max_value(sequence, fade_fcurve)

        if type == "IN":
            self.start = Vector((sequence.frame_final_start, 0.0))
            self.end = Vector((sequence.frame_final_start + self.duration, self.max_value))
        elif type == "OUT":
            self.start = Vector((sequence.frame_final_end - self.duration, self.max_value))
            self.end = Vector((sequence.frame_final_end, 0.0))

    def calculate_max_value(self, sequence, fade_fcurve):
        """
        Returns the maximum Y coordinate the fade animation should use for a given sequence
        Uses either the sequence's value for the animated property, or the next keyframe after the fade
        """
        max_value = 0.0

        if not fade_fcurve.keyframe_points:
            max_value = getattr(sequence, self.animated_property, 1.0)
        else:
            if self.type == "IN":
                fade_end = sequence.frame_final_start + self.duration
                keyframes = (k for k in fade_fcurve.keyframe_points if k.co[0] >= fade_end)
            if self.type == "OUT":
                fade_start = sequence.frame_final_end - self.duration
                keyframes = (
                    k for k in reversed(fade_fcurve.keyframe_points) if k.co[0] <= fade_start
                )
            try:
                max_value = next(keyframes).co[1]
            except StopIteration:
                pass

        return max_value if max_value > 0.0 else 1.0

    def __repr__(self):
        return "Fade {}: {} to {}".format(self.type, self.start, self.end)


def calculate_duration_frames(context, duration_seconds):
    return round(duration_seconds * context.scene.render.fps / context.scene.render.fps_base)
