dracula-musical/src/main/kotlin/de/moritzruth/theaterdsl/DynamicValue.kt

package de.moritzruth.theaterdsl

import de.moritzruth.theaterdsl.value.*
import kotlinx.collections.immutable.ImmutableList
import kotlinx.collections.immutable.persistentListOf
import kotlinx.collections.immutable.toImmutableList
import kotlin.math.PI
import kotlin.math.asin
import kotlin.math.min
import kotlin.math.sin
import kotlin.time.Duration
import kotlin.time.ExperimentalTime
import kotlin.time.TimeSource

interface DynamicValue<T> {
    fun getCurrentValue(): T
}

@OptIn(ExperimentalTime::class)
class PercentageDV(initialStaticValue: Percentage = 0.percent): DynamicValue<Percentage> {
    private sealed interface State {
        data class Static(val value: Percentage): State

        data class Fade(val start: Percentage, val end: Percentage, val duration: Duration): State {
            val delta = end.value - start.value
        }

        data class Sine(
            val offset: Double,
            val minimum: Percentage,
            val maximum: Percentage,
            val period: Duration
        ): State {
            companion object {
                fun calculateA(minimum: Percentage, maximum: Percentage) = (maximum.value - minimum.value) * 0.5
                fun calculateX(progress: Double, offset: Double) = 2 * PI * progress - offset
                fun calculateD(minimum: Percentage) = 0.5 + minimum.value
            }
        }

        data class Step(val steps: ImmutableList<Percentage>, val interval: Duration, val startIndex: Int): State
    }

    private var stateChangeMark = TimeSource.Monotonic.markNow()
    private var state: State = State.Static(initialStaticValue)
        set(value) {
            field = value
            stateChangeMark = TimeSource.Monotonic.markNow()
        }

    override fun getCurrentValue(): Percentage {
        val elapsedTime = stateChangeMark.elapsedNow()

        return when (val s = state) {
            is State.Static -> s.value
            is State.Fade -> (min(elapsedTime / s.duration, 1.0) * s.delta + s.start.value).toFloat().asPercentage()
            is State.Sine -> {
                val a = State.Sine.calculateA(s.minimum, s.maximum)
                val x = State.Sine.calculateX(elapsedTime / s.period, s.offset)
                val d = State.Sine.calculateD(s.minimum)

                (a * sin(x) + d).toFloat().asPercentage()
            }
            is State.Step -> {
                val index = (elapsedTime / s.interval).toInt() + s.startIndex
                s.steps[index.mod(s.steps.size)]
            }
        }
    }

    fun static(value: Percentage) {
        state = State.Static(value)
    }

    fun fade(end: Percentage, duration: Duration, start: Percentage = getCurrentValue()) {
        state = State.Fade(start, end, duration)
    }

    fun sine(minimum: Percentage, maximum: Percentage, period: Duration, start: Percentage = getCurrentValue()) {
        val offset = asin((start.value - State.Sine.calculateD(minimum)) / State.Sine.calculateA(minimum, maximum))
        state = State.Sine(offset, minimum, maximum, period)
    }

    fun steps(steps: List<Percentage>, interval: Duration, startIndex: Int = 0) {
        state = State.Step(steps.toImmutableList(), interval, startIndex)
    }

    fun switch(a: Percentage, b: Percentage, interval: Duration, startAtCurrent: Boolean = true) {
        val startIndex = startAtCurrent
            .takeIf { it }
            ?.let { getCurrentValue() }
            ?.takeIf { it == b }
            ?.let { 1 } ?: 0

        steps(persistentListOf(a, b), interval, startIndex)
    }
}

@OptIn(ExperimentalTime::class)
class ColorDV(initialStaticValue: Color = Color.WHITE): DynamicValue<Color> {
    private sealed interface State {
        data class Static(val value: Color): State
        data class Fade(val start: Color, val end: Color, val duration: Duration): State {
            val deltaHue = ((end.hue.degree - start.hue.degree).mod(360f) + 540f).mod(360f) - 180f
            val deltaSaturation = end.saturation.value - start.saturation.value
            val deltaBrightness = end.brightness.value - start.brightness.value
        }
    }

    private var stateChangeMark = TimeSource.Monotonic.markNow()
    private var state: State = State.Static(initialStaticValue)
        set(value) {
            field = value
            stateChangeMark = TimeSource.Monotonic.markNow()
        }

    override fun getCurrentValue(): Color {
        val elapsedTime = stateChangeMark.elapsedNow()

        return when(val s = state) {
            is State.Static -> s.value
            is State.Fade -> {
                val progress = min(elapsedTime / s.duration, 1.0)

                Color(
                    hue = Angle((s.start.hue.degree + s.deltaHue * progress).toFloat()),
                    saturation = Percentage((s.start.saturation.value + s.deltaSaturation * progress).toFloat()),
                    brightness = Percentage((s.start.brightness.value + s.deltaBrightness * progress).toFloat())
                )
            }
        }
    }

    fun static(value: Color) {
        state = State.Static(value)
    }

    fun fade(end: Color, duration: Duration, start: Color = getCurrentValue()) {
        state = State.Fade(start, end, duration)
    }
}