import SwiftUI

struct WatchBeforeAfterFlowView: View {
  enum Stage { case intro, before, beforeFeeling, exercise, after, afterFeeling, result }

  @EnvironmentObject private var model: WatchAppModel
  let regulation: WatchRegulationProtocol
  @State private var stage: Stage = .intro
  @State private var before: WatchMeasurementSummaryV1?
  @State private var after: WatchMeasurementSummaryV1?
  @State private var exerciseStartedAt: Date?
  @State private var flowError: String?
  @State private var selectedFeeling = 3
  @State private var feelingBefore: Int?
  @State private var feelingAfter: Int?

  var body: some View {
    ScrollView {
      VStack(spacing: 10) {
        switch stage {
        case .intro:
          Image(systemName: "arrow.left.arrow.right.heart.fill").font(.title).foregroundStyle(WatchTheme.accent)
          Text("Avant · Exercice · Après").font(.headline).multilineTextAlignment(.center)
          Text("Deux mesures identiques encadrent l’exercice pour comparer le BPM et la qualité, sans score de stress.")
            .font(.caption2).foregroundStyle(WatchTheme.secondary).multilineTextAlignment(.center)
          Button("Mesurer avant") { startMeasurement(stage: .before) }.buttonStyle(.borderedProminent)
        case .before, .after:
          measurementContent
        case .beforeFeeling:
          feelingContent(title: "Comment vous sentez-vous avant ?") {
            feelingBefore = selectedFeeling
            if var measurement = before {
              measurement.feeling = selectedFeeling
              measurement.feelingRecordedAt = Date()
              measurement.updatedAt = Date()
              before = measurement
              model.enqueueMeasurement(measurement)
            }
            stage = .exercise
            exerciseStartedAt = Date()
            Task {
              do { try await model.haptics.start(protocol: regulation) }
              catch { flowError = error.localizedDescription }
            }
          }
        case .exercise:
          if model.haptics.isRunning, let exerciseStartedAt {
            BreathOrb(regulation: regulation, startedAt: exerciseStartedAt)
            ProgressView(value: model.haptics.elapsedSeconds, total: regulation.durationSeconds)
            Button("Arrêter", role: .cancel) { model.haptics.cancel() }
          } else {
            Text("Exercice terminé").font(.headline)
            Button("Mesurer après") { startMeasurement(stage: .after) }.buttonStyle(.borderedProminent)
          }
        case .afterFeeling:
          feelingContent(title: "Comment vous sentez-vous après ?") {
            feelingAfter = selectedFeeling
            if var measurement = after {
              measurement.feeling = selectedFeeling
              measurement.feelingRecordedAt = Date()
              measurement.updatedAt = Date()
              after = measurement
              model.enqueueMeasurement(measurement)
            }
            saveCompletedSession()
            stage = .result
          }
        case .result:
          resultContent
        }
        if let flowError { Text(flowError).font(.caption2).foregroundStyle(.orange) }
      }
      .padding(.horizontal, 4)
    }
    .navigationTitle("Comparaison")
    .haptikaScreen()
    .onChange(of: model.measurement.state) { _, newState in handleMeasurementState(newState) }
  }

  @ViewBuilder
  private var measurementContent: some View {
    switch model.measurement.state {
    case let .waitingForFirstSample(seconds):
      ProgressView()
      Text("Recherche du signal · \(seconds) s").font(.caption2)
    case let .collecting(progress):
      Text(model.measurement.currentBPM.map { "\(Int($0.rounded())) BPM" } ?? "— BPM").font(.title2.bold())
      ProgressView(value: progress)
      Text(stage == .before ? "Mesure avant" : "Mesure après").font(.caption2)
    case .finishing:
      ProgressView("Analyse…")
    default:
      ProgressView()
    }
    Button("Annuler", role: .cancel) { model.measurement.cancel(); stage = .intro }
  }

  private var resultContent: some View {
    VStack(spacing: 9) {
      Text("Votre comparaison").font(.headline)
      WatchCard {
        VStack(alignment: .leading, spacing: 5) {
          metricRow("Avant", before?.averageBPM)
          metricRow("Après", after?.averageBPM)
          if let beforeBPM = before?.averageBPM, let afterBPM = after?.averageBPM {
            Divider()
            Text(String(format: "Écart %+.0f BPM", afterBPM - beforeBPM)).foregroundStyle(WatchTheme.accent)
          }
          Text("Qualité : \(Int(((before?.quality ?? 0) * 100).rounded())) % → \(Int(((after?.quality ?? 0) * 100).rounded())) %")
          if let feelingBefore, let feelingAfter {
            Text("Ressenti : \(feelingBefore)/5 → \(feelingAfter)/5")
          }
        }
        .font(.caption)
      }
      Text("Une variation ponctuelle n’est pas un diagnostic.").font(.caption2).foregroundStyle(WatchTheme.secondary)
    }
  }

  private func metricRow(_ label: String, _ bpm: Double?) -> some View {
    HStack {
      Text(label)
      Spacer()
      Text(bpm.map { "\(Int($0.rounded())) BPM" } ?? "—")
    }
  }

  private func startMeasurement(stage: Stage) {
    self.stage = stage
    model.measurement.resetAfterResult()
    Task {
      do {
        try await model.measurement.requestAuthorization()
        try await model.measurement.start()
      } catch { flowError = error.localizedDescription }
    }
  }

  private func feelingContent(title: String, onConfirm: @escaping () -> Void) -> some View {
    VStack(spacing: 10) {
      Text(title).font(.headline).multilineTextAlignment(.center)
      Picker("Ressenti", selection: $selectedFeeling) {
        ForEach(1...5, id: \.self) { score in Text("\(score) / 5").tag(score) }
      }
      Button("Continuer", action: onConfirm).buttonStyle(.borderedProminent)
    }
  }

  private func saveCompletedSession() {
    let endedAt = Date()
    model.enqueueSession(.init(
      protocolID: regulation.id,
      startedAt: exerciseStartedAt ?? endedAt,
      endedAt: endedAt,
      durationSeconds: regulation.durationSeconds,
      state: .completed,
      beforeMeasurementID: before?.id,
      afterMeasurementID: after?.id,
      feelingBefore: feelingBefore,
      feelingAfter: feelingAfter
    ))
  }

  private func handleMeasurementState(_ state: WatchMeasurementState) {
    guard case let .completed(summary) = state else { return }
    if stage == .before {
      before = summary
      model.measurement.resetAfterResult()
      selectedFeeling = 3
      stage = .beforeFeeling
    } else if stage == .after {
      after = summary
      model.measurement.resetAfterResult()
      selectedFeeling = 3
      stage = .afterFeeling
    }
  }
}