VesiscanClinicalAndroid/app/src/main/java/com/example/medilightv2android/managers/BackReflection.kt

package com.example.medilightv2android.managers

import kotlin.math.abs
import kotlin.math.max
import kotlin.math.min
import kotlin.math.roundToInt

/**
 * 후면반사 탐지+제거 시스템 — Python span_utils.py + pipeline.py 1:1 포팅
 *
 * 흐름: build_candidate → consensus → is_reflection_only → resolve → suppress → rerun → choose
 */
object BackReflection {

    private const val MIN_BACK_REFLECTION_PROM = 50.0
    private const val POST_MATCH_TOL = 3
    private const val OUTLIER_TOL = 4
    private const val SHARED_TOL = 3
    private const val MIN_CHANNELS = 3
    private const val RADIUS = 6
    private const val EXTEND = 20

    // ── Valley helpers (50.0 rise early-stop) ──

    private fun findLeftValleyValue(x: DoubleArray, peakIdx: Int, maxDist: Int = 20): Double {
        var v = x[peakIdx]
        for (i in (peakIdx - 1) downTo max(0, peakIdx - maxDist)) {
            val cur = x[i]
            if (cur < v) v = cur
            else if (cur > v + 50.0) break
        }
        return v
    }

    private fun findRightValleyValue(x: DoubleArray, peakIdx: Int, maxDist: Int = 20): Double {
        var v = x[peakIdx]
        for (i in (peakIdx + 1) until min(x.size, peakIdx + maxDist + 1)) {
            val cur = x[i]
            if (cur < v) v = cur
            else if (cur > v + 50.0) break
        }
        return v
    }

    // ── Strongest significant peak ──

    private fun strongestSignificantPeak(x: DoubleArray, lo: Int, hi: Int, minProm: Double = MIN_BACK_REFLECTION_PROM): Int? {
        if (lo >= hi || lo < 0 || hi > x.size) return null
        val seg: DoubleArray = x.sliceArray(lo until hi)
        val peaks: List<Int> = PiezoEchoAnalyzer.shared.findPeaks1D(seg)
        if (peaks.isEmpty()) return null

        var bestIdx: Int? = null
        var bestAmp = Double.NEGATIVE_INFINITY
        for (p: Int in peaks) {
            val gp = p + lo
            val leftV = findLeftValleyValue(x, gp)
            val rightV = findRightValleyValue(x, gp)
            val prom = x[gp] - min(leftV, rightV)
            if (prom < minProm) continue
            if (x[gp] > bestAmp) { bestAmp = x[gp]; bestIdx = gp }
        }
        return bestIdx
    }

    // ── find_back_reflection_idx (legacy, 전체 범위) ──

    fun findBackReflectionIdx(tgcSg: DoubleArray, postMaxIdx: Int, minSearchIdx: Int = 40, extend: Int = EXTEND): Int {
        val n = tgcSg.size
        val searchEnd = min(n, postMaxIdx + extend)
        if (minSearchIdx >= searchEnd) return postMaxIdx
        val seg: DoubleArray = tgcSg.sliceArray(minSearchIdx until searchEnd)
        val peaks: List<Int> = PiezoEchoAnalyzer.shared.findPeaks1D(seg)
        if (peaks.isEmpty()) return postMaxIdx
        val globalPeaks: List<Int> = peaks.map { p -> p + minSearchIdx }
        return globalPeaks.maxByOrNull { idx -> tgcSg[idx] } ?: postMaxIdx
    }

    // ── find_back_reflection_after_post ──

    fun findBackReflectionAfterPost(tgcSg: DoubleArray, postIdx: Int, postMaxIdx: Int, extend: Int = EXTEND): Int? {
        val searchStart = postIdx + 1
        val searchEnd = min(tgcSg.size, postMaxIdx + extend)
        if (searchStart >= searchEnd) return null
        return strongestSignificantPeak(tgcSg, searchStart, searchEnd)
    }

    // ── find_back_reflection_near_idx ──

    fun findBackReflectionNearIdx(tgcSg: DoubleArray, centerIdx: Int, postIdx: Int, postMaxIdx: Int, radius: Int = RADIUS, extend: Int = EXTEND): Int? {
        val n = tgcSg.size
        val lo = max(postIdx + 1, centerIdx - radius)
        val hi = min(n, min(postMaxIdx + extend, centerIdx + radius + 1))
        if (lo >= hi) return null
        return strongestSignificantPeak(tgcSg, lo, hi)
    }

    // ── build_back_reflection_candidate ──

    fun buildCandidate(tgcSg: DoubleArray, postIdx: Int, postMaxIdx: Int, postMatchTol: Int = POST_MATCH_TOL): Int? {
        val globalBr = findBackReflectionIdx(tgcSg, postMaxIdx)
        if (abs(globalBr - postIdx) <= postMatchTol) return null  // 후위벽≈전체BR → 별도 BR 없음
        return findBackReflectionAfterPost(tgcSg, postIdx, postMaxIdx)
    }

    // ── consensus_back_reflection_idx ──

    private const val MIN_VOTES = 3
    private const val AMP_RATIO = 1.5

    fun consensusIdx(candidates: List<Int?>, outlierTol: Int = OUTLIER_TOL, minVotes: Int = MIN_VOTES): Int? {
        val vals = candidates.filterNotNull()
        if (vals.size < minVotes) return null
        val sorted = vals.sorted()
        val med = sorted[sorted.size / 2].toDouble()
        val inliers = vals.filter { abs(it - med) <= outlierTol }
        val finalVals = inliers.ifEmpty { vals }
        val finalSorted = finalVals.sorted()
        return finalSorted[finalSorted.size / 2]
    }

    // ── is_suspicious_post_peak ──

    fun isSuspiciousPostPeak(tgcSg: DoubleArray, postIdx: Int, antIdx: Int? = null, sharedIdx: Int? = null, sharedTol: Int = 2, ampRatio: Double = AMP_RATIO): Boolean {
        val n = tgcSg.size
        if (postIdx < 0 || postIdx >= n) return false
        var suspicious = false
        if (antIdx != null && antIdx in 0 until n && tgcSg[postIdx] > tgcSg[antIdx] * ampRatio) suspicious = true
        if (sharedIdx != null && abs(postIdx - sharedIdx) <= sharedTol) suspicious = true
        return suspicious
    }

    // ── select_back_reflection_idx ──

    fun selectIdx(tgcSg: DoubleArray, postIdx: Int, postMaxIdx: Int, antIdx: Int? = null, sharedIdx: Int? = null, channelCandidate: Int? = null): Int? {
        val suspiciousPost = isSuspiciousPostPeak(tgcSg, postIdx, antIdx = antIdx, sharedIdx = sharedIdx)

        var local: Int? = null
        if (sharedIdx != null) {
            local = findBackReflectionNearIdx(tgcSg, sharedIdx, postIdx, postMaxIdx)
        }

        if (suspiciousPost && sharedIdx != null) {
            val postDist = abs(postIdx - sharedIdx)
            val localDist = local?.let { abs(it - sharedIdx) }
            val candDist = channelCandidate?.let { abs(it - sharedIdx) }
            var nearestOther: Int? = localDist
            if (candDist != null) nearestOther = if (nearestOther == null) candDist else min(nearestOther, candDist)
            if (nearestOther == null || postDist < nearestOther) return postIdx
        }

        if (local != null) return local
        if (channelCandidate != null) return channelCandidate
        if (suspiciousPost) return postIdx
        return null
    }

    // ── resolve_back_reflection_indices ──

    data class ResolveResult(val brIdx: Int?, val suppressIdx: Int?)

    fun resolveIndices(tgcSg: DoubleArray, postIdx: Int, postMaxIdx: Int, antIdx: Int? = null, sharedIdx: Int? = null, channelCandidate: Int? = null): ResolveResult {
        val br = selectIdx(tgcSg, postIdx, postMaxIdx, antIdx = antIdx, sharedIdx = sharedIdx, channelCandidate = channelCandidate)
            ?: return ResolveResult(null, null)
        val suppressIdx = sharedIdx ?: br
        return ResolveResult(br, suppressIdx)
    }

    // ── is_reflection_only_multichannel ──

    fun isReflectionOnlyMultichannel(
        tgcSignals: List<DoubleArray>,
        wallPairs: List<Pair<Int?, Int?>>,
        sharedIdx: Int? = null,
        sharedTol: Int = SHARED_TOL,
        minChannels: Int = MIN_CHANNELS,
        ampRatio: Double = AMP_RATIO
    ): Boolean {
        data class Valid(val i: Int, val ant: Int, val post: Int)
        val valid = wallPairs.mapIndexedNotNull { i, (ant, post) ->
            if (ant != null && post != null) Valid(i, ant, post) else null
        }
        if (valid.size < minChannels) return false
        val ratio = ampRatio

        // 조건 A: shared_idx 기반
        var effectiveShared = sharedIdx
        if (effectiveShared == null) {
            val postVals = valid.map { it.post }.sorted()
            val med = postVals[postVals.size / 2].toDouble()
            val inliers = valid.filter { abs(it.post - med) <= sharedTol }
            if (inliers.size >= minChannels) effectiveShared = med.roundToInt()
        }
        if (effectiveShared != null) {
            if (valid.all { abs(it.post - effectiveShared!!) <= sharedTol && tgcSignals[it.i][it.post] > tgcSignals[it.i][it.ant] * ratio }) return true
        }

        // 조건 B: post 클러스터
        val postVals = valid.map { it.post }.sorted()
        val medPost = postVals[postVals.size / 2].toDouble()
        val inlierTriples = valid.filter { abs(it.post - medPost) <= sharedTol }
        if (inlierTriples.size >= minChannels) {
            if (inlierTriples.all { tgcSignals[it.i][it.post] > tgcSignals[it.i][it.ant] * ratio }) return true
        }
        return false
    }

    // ── choose_rerun_or_initial_result ──

    fun chooseResult(
        initial: LowEchoResult?, rerun: LowEchoResult?,
        brIdx: Int?, suppressIdx: Int?,
        minGap: Int, minBrSep: Int = 0, minInitialUrineLen: Int = 0
    ): LowEchoResult? {
        if (rerun != null) return rerun
        if (canFallbackToInitial(initial, brIdx, suppressIdx, minGap, minBrSep, minInitialUrineLen)) return initial
        return null
    }

    private fun canFallbackToInitial(initial: LowEchoResult?, brIdx: Int?, suppressIdx: Int?, minGap: Int, minBrSep: Int, minInitialUrineLen: Int): Boolean {
        if (initial == null || brIdx == null || suppressIdx == null) return false
        if (abs(brIdx - initial.post) < minBrSep) return false
        if ((suppressIdx - initial.post) < minGap) return false
        if (initial.urineLen < minInitialUrineLen) return false
        return true
    }

    // ── suppress_back_reflection (valley early-stop 50.0) ──

    fun suppress(sg: DoubleArray, backRefIdx: Int, searchMargin: Int = 10): DoubleArray {
        val cleaned = sg.copyOf()
        val n = sg.size
        if (backRefIdx >= n) return cleaned

        val lo = max(0, backRefIdx - min(searchMargin, 3))
        val hi = min(n, backRefIdx + searchMargin + 1)
        var actualPeak = lo
        for (i in lo until hi) if (sg[i] > sg[actualPeak]) actualPeak = i

        // Left valley with 50.0 rise early-stop
        var leftValley = actualPeak
        var leftBest = sg[actualPeak]
        for (i in (actualPeak - 1) downTo max(0, actualPeak - searchMargin)) {
            val cur = sg[i]
            if (cur < leftBest) { leftBest = cur; leftValley = i }
            else if (cur > leftBest + 50.0) break
        }

        // Right valley with 50.0 rise early-stop
        var rightValley = actualPeak
        var rightBest = sg[actualPeak]
        for (i in (actualPeak + 1) until min(n, actualPeak + searchMargin + 1)) {
            val cur = sg[i]
            if (cur < rightBest) { rightBest = cur; rightValley = i }
            else if (cur > rightBest + 50.0) break
        }

        if (rightValley > leftValley) {
            val leftVal = sg[leftValley]
            val rightVal = sg[rightValley]
            val length = rightValley - leftValley
            for (i in 0..length) {
                cleaned[leftValley + i] = leftVal + (rightVal - leftVal) * i.toDouble() / length
            }
        }
        return cleaned
    }
}