//
// RunFlowView.swift
// Workouts Watch App
//
// Copyright 2025 Rouslan Zenetl. All Rights Reserved.
//

import SwiftUI

/// Thin coordinator that lets a single pushed run walk across exercises in a flow-mode
/// split (`autoAdvance`). It owns which log is on screen and swaps it when the running
/// `ExerciseProgressView` finishes an exercise; `.id(currentLogID)` rebuilds the child
/// fresh for each exercise, so the delicate per-exercise run/mirror machinery stays
/// exactly as it is. For a non-flow split it's transparent — one exercise, unchanged.
struct RunFlowView: View {
    @Environment(WatchConnectivityBridge.self) private var bridge

    @Binding var doc: WorkoutDocument
    let startLogID: String
    let onChange: () -> Void
    let onLive: (LiveProgress) -> Void
    /// Send the "stop mirroring this run" signal for a given log — parameterized because
    /// the run's current log advances; the leaving exercise's id is what ends.
    let sendLiveEnded: (String) -> Void

    @State private var currentLogID: String
    /// True once we've auto-advanced at least once — the current exercise then skips its
    /// Ready page and begins on appear. The first exercise (manual entry) keeps Ready.
    @State private var enteredViaFlow = false
    /// Set across an exercise hand-off so the leaving exercise's teardown doesn't tear the
    /// mirror down — the run is continuing, not ending.
    @State private var advancing = false

    init(doc: Binding<WorkoutDocument>, startLogID: String, onChange: @escaping () -> Void,
         onLive: @escaping (LiveProgress) -> Void, sendLiveEnded: @escaping (String) -> Void) {
        self._doc = doc
        self.startLogID = startLogID
        self.onChange = onChange
        self.onLive = onLive
        self.sendLiveEnded = sendLiveEnded
        _currentLogID = State(initialValue: startLogID)
    }

    var body: some View {
        // The ZStack is a stable identity (its lifecycle fires once for the whole run),
        // while the child re-identifies per exercise via `.id(currentLogID)`.
        ZStack {
            ExerciseProgressView(
                doc: $doc,
                logID: currentLogID,
                onChange: onChange,
                onLive: onLive,
                onLiveEnded: { if !advancing { sendLiveEnded(currentLogID) } },
                incomingFrame: bridge.liveIncoming.flatMap { $0.logID == currentLogID ? $0 : nil },
                enteredViaFlow: enteredViaFlow,
                onAdvance: advance(to:)
            )
            .id(currentLogID)
        }
        .onAppear { bridge.navigatedRunID = currentLogID }
        .onDisappear { if bridge.navigatedRunID == currentLogID { bridge.navigatedRunID = nil } }
    }

    /// Hand off to the next exercise. Suppresses the leaving exercise's live-ended teardown
    /// so the mirror follows across the boundary, moves `navigatedRunID` forward so this
    /// device doesn't mirror its own next exercise, then swaps the presented log.
    private func advance(to next: String) {
        advancing = true
        bridge.navigatedRunID = next
        enteredViaFlow = true
        currentLogID = next
        // Release the guard after the swap settles (old view torn down, new one begun).
        Task { @MainActor in advancing = false }
    }
}