/**
 * 铸爱流程中的光栅预览：与 lenticular-studio 一致的物理参数、离散档位与陀螺仪启动节奏
 */
import { ref, nextTick } from 'vue'
import { useLenticularPreview } from '@/composables/useLenticularPreview.js'
import { useLenticularStudioTilt } from '@/composables/useLenticularStudioTilt.js'

const FLOW_PHYSICS = {
	angleStability: 52,
	transitionSmoothness: 40,
	tiltSensitivity: 96,
	sensorDeadzoneStrength: 0,
	parallaxDepth: 18,
	lenticularAnchorFloor: 0.1,
	lenticularNonDominantResidualMin: 0.092,
	lenticularPrevLayerGhostMin: 0.098,
	lenticularBlendBaseScale: 1.1,
}

const DISCRETE_STEP_DEG = 13
const DISCRETE_STEP_HYST_DEG = 5
const TILT_MAG_TAU_MS = 150
const TILT_MAG_MAX_RISE_DPS = 82
const TILT_MAG_MAX_FALL_DPS = 168
const TILT_AWAY_FROM_LEVEL_DPS = 72
const TILT_RISE_TIGHTEN = 0.42
export const LENTICULAR_TILT_START_DELAY_MS = 560

/**
 * @param {import('vue').Ref<Array>|import('vue').Ref<unknown>} layersRef
 */
export function useLenticularCraftTiltPreview(layersRef) {
	const gyroSourceLabel = ref('simulation')
	const { physics, layerTransforms, simulate, relax, snapSimulatedTilt } = useLenticularPreview(layersRef)
	Object.assign(physics, FLOW_PHYSICS)

	const discreteStableStep = ref(0)
	let tiltMagEma = 0
	let lastTiltMagSampleAt = 0
	let lastSignedDegHint = null

	function resetTiltMagFilter() {
		tiltMagEma = 0
		lastTiltMagSampleAt = 0
		lastSignedDegHint = null
	}

	function getLayersArray() {
		const v = layersRef.value !== undefined ? layersRef.value : layersRef
		return Array.isArray(v) ? v : []
	}

	function simulateFromSignedDegrees(tiltMagDeg, signedDegHint) {
		const ls = getLayersArray()
		const n = Math.max(1, ls.length)
		const raw = Math.abs(Number(tiltMagDeg) || 0)
		const now = Date.now()
		let dt = 33
		if (lastTiltMagSampleAt > 0) {
			dt = now - lastTiltMagSampleAt
		}
		lastTiltMagSampleAt = now
		dt = Math.max(16, Math.min(100, dt))
		const alpha = 1 - Math.exp(-dt / TILT_MAG_TAU_MS)
		let nextEma = tiltMagEma + (raw - tiltMagEma) * alpha

		const sec = dt * 0.001
		let maxRise = TILT_MAG_MAX_RISE_DPS * sec
		const maxFall = TILT_MAG_MAX_FALL_DPS * sec

		if (Number.isFinite(signedDegHint)) {
			if (lastSignedDegHint != null && sec > 1e-6) {
				const dAbsSignedDt =
					(Math.abs(signedDegHint) - Math.abs(lastSignedDegHint)) / sec
				if (dAbsSignedDt > TILT_AWAY_FROM_LEVEL_DPS) {
					maxRise *= TILT_RISE_TIGHTEN
				}
			}
			lastSignedDegHint = signedDegHint
		} else {
			lastSignedDegHint = null
		}

		let dMag = nextEma - tiltMagEma
		if (dMag > 0) {
			dMag = Math.min(dMag, maxRise)
		} else {
			dMag = Math.max(dMag, -maxFall)
		}
		tiltMagEma += dMag

		const absDeg = tiltMagEma
		const STEP = DISCRETE_STEP_DEG
		const MARGIN = DISCRETE_STEP_HYST_DEG
		const stepBefore = discreteStableStep.value
		let s = stepBefore
		while (absDeg >= (s + 1) * STEP + MARGIN) s++
		while (s > 0 && absDeg <= s * STEP - MARGIN) s--
		discreteStableStep.value = s
		const idx = s % n
		const sens = physics.tiltSensitivity / 100
		const mul = 0.44 + sens * 0.52
		const u = (idx + 0.5) / n
		const gPick = Math.max(-1, Math.min(1, 2 * u - 1))
		const gamma = Math.max(-1, Math.min(1, gPick / mul))
		simulate(gamma, 0)
	}

	function lockPreviewStill() {
		discreteStableStep.value = 0
		resetTiltMagFilter()
		simulateFromSignedDegrees(0)
		snapSimulatedTilt({ resetLayerSmoothing: true })
	}

	const { start: startTilt, stop: stopTilt } = useLenticularStudioTilt({
		simulate,
		simulateFromSignedDegrees,
		gyroSourceLabel,
		useStudioAccelDirect: true,
		onTiltDriverFallback: () => {
			discreteStableStep.value = 0
			resetTiltMagFilter()
		},
	})

	let entryTiltTimer = null

	function cancelScheduledTiltStart() {
		if (entryTiltTimer != null) {
			clearTimeout(entryTiltTimer)
			entryTiltTimer = null
		}
	}

	function scheduleTiltStart() {
		cancelScheduledTiltStart()
		nextTick(() => {
			relax(0.86)
			lockPreviewStill()
			entryTiltTimer = setTimeout(() => {
				entryTiltTimer = null
				startTilt()
			}, LENTICULAR_TILT_START_DELAY_MS)
		})
	}

	function stopTiltPreview() {
		cancelScheduledTiltStart()
		stopTilt()
	}

	return {
		physics,
		layerTransforms,
		simulate,
		relax,
		gyroSourceLabel,
		scheduleTiltStart,
		stopTiltPreview,
		lockPreviewStill,
	}
}