//
// ExerciseLibraryView.swift
// Workouts
//
// Copyright 2026 Rouslan Zenetl. All Rights Reserved.
//

import SwiftUI
import SwiftData

/// The Exercises library screen, pushed from Settings → Library: every exercise with
/// a bundled motion rig (the same catalog the picker offers), each opening its
/// reference page.
struct ExerciseLibraryView: View {
    var body: some View {
        List(ExerciseMotionLibrary.exerciseNames, id: \.self) { name in
            NavigationLink(name) {
                ExerciseLibraryDetailView(exerciseName: name)
            }
        }
        .navigationTitle("Exercises")
    }
}

/// One library exercise, in the standard half-and-half exercise layout: the top half
/// scrolls the user's machine settings (their setup cheat-sheet), the authored
/// reference content (summary, targets, setup/execution/cues…), and the weight
/// progression chart; the looping form-guide figure holds the bottom.
struct ExerciseLibraryDetailView: View {
    let exerciseName: String

    /// This exercise wherever it appears in the user's splits — the source of the
    /// recorded machine settings.
    @Query private var exercises: [Exercise]

    /// One completed weighted log is enough to justify the progression chart;
    /// bodyweight and timed exercises never accrue one, so they skip the chart
    /// instead of plotting a flat zero line.
    @Query private var weightedLogs: [WorkoutLog]

    init(exerciseName: String) {
        self.exerciseName = exerciseName
        let name = exerciseName
        _exercises = Query(filter: #Predicate<Exercise> { $0.name == name })
        let completedRaw = WorkoutStatus.completed.rawValue
        _weightedLogs = Query(filter: #Predicate<WorkoutLog> {
            $0.exerciseName == name && $0.statusRaw == completedRaw && $0.weight > 0
        })
    }

    private var info: ExerciseInfo? {
        ExerciseInfoLibrary.info(for: exerciseName)
    }

    /// Distinct recorded machine-settings lists for this exercise. Usually one; when
    /// splits disagree, each distinct list keeps its split's name as a label.
    private var settingsGroups: [(label: String?, settings: [MachineSetting])] {
        var groups: [(label: String?, settings: [MachineSetting])] = []
        for exercise in exercises {
            guard let settings = exercise.machineSettings, !settings.isEmpty else { continue }
            guard !groups.contains(where: { $0.settings == settings }) else { continue }
            groups.append((exercise.split?.name, settings))
        }
        if groups.count == 1 { groups[0].label = nil }
        return groups
    }

    var body: some View {
        VStack(spacing: 0) {
            ScrollView {
                VStack(alignment: .leading, spacing: 16) {
                    // Show the card whenever settings are recorded — or, for an
                    // exercise the authored info identifies as machine-based, as an
                    // empty state, so the feature is discoverable before first use.
                    if !settingsGroups.isEmpty {
                        MachineSettingsCard(groups: settingsGroups)
                    } else if info?.isMachineBased == true {
                        MachineSettingsCard(groups: [])
                    }
                    if let info {
                        ExerciseInfoContent(info: info)
                    }
                    if !weightedLogs.isEmpty {
                        WeightProgressionChartView(exerciseName: exerciseName)
                    }
                }
                .padding()
                .frame(maxWidth: .infinity, alignment: .leading)
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)

            ExerciseFigureSlot(exerciseName: exerciseName)
        }
        .navigationTitle(exerciseName)
        .navigationBarTitleDisplayMode(.inline)
    }
}

/// The user's recorded machine comfort settings, set apart from the reference text
/// as a card: name–value rows, grouped per split when the recorded lists differ.
/// Empty `groups` renders the not-yet-recorded state (shown for machine-based
/// exercises so the feature is visible before first use).
private struct MachineSettingsCard: View {
    let groups: [(label: String?, settings: [MachineSetting])]

    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("Your Machine Settings")
                .font(.headline)
            if groups.isEmpty {
                Text("None recorded yet. Mark the exercise as machine-based in its editor, or use the settings button on the workout screen.")
                    .font(.callout)
                    .foregroundStyle(.secondary)
            }
            ForEach(Array(groups.enumerated()), id: \.offset) { _, group in
                VStack(alignment: .leading, spacing: 4) {
                    if let label = group.label {
                        Text(label)
                            .font(.caption)
                            .foregroundStyle(.secondary)
                    }
                    ForEach(Array(group.settings.enumerated()), id: \.offset) { _, setting in
                        HStack(alignment: .firstTextBaseline) {
                            Text(setting.name)
                                .foregroundStyle(.secondary)
                            Spacer()
                            Text(setting.value)
                                .fontWeight(.semibold)
                                .monospacedDigit()
                        }
                        .font(.callout)
                    }
                }
            }
        }
        .padding(12)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(Color(.secondarySystemBackground), in: RoundedRectangle(cornerRadius: 12))
    }
}

/// Renders a parsed `ExerciseInfo`: summary, target chips, then each authored
/// section with its numbered steps or bullets.
private struct ExerciseInfoContent: View {
    let info: ExerciseInfo

    var body: some View {
        VStack(alignment: .leading, spacing: 16) {
            if !info.summary.isEmpty {
                Text(info.summary)
                    .font(.callout)
                    .foregroundStyle(.secondary)
            }

            if !info.targets.isEmpty {
                TargetChips(targets: info.targets)
            }

            ForEach(info.sections, id: \.title) { section in
                VStack(alignment: .leading, spacing: 6) {
                    Text(section.title)
                        .font(.headline)
                    ForEach(Array(section.items.enumerated()), id: \.offset) { index, item in
                        itemRow(item, ordinal: ordinal(for: item, at: index, in: section))
                    }
                }
            }
        }
    }

    /// Steps number themselves by their position among the section's steps, so an
    /// interleaved paragraph doesn't break the count.
    private func ordinal(for item: ExerciseInfo.Item, at index: Int, in section: ExerciseInfo.Section) -> Int? {
        guard case .step = item else { return nil }
        return section.items[...index].reduce(0) { count, it in
            if case .step = it { count + 1 } else { count }
        }
    }

    @ViewBuilder
    private func itemRow(_ item: ExerciseInfo.Item, ordinal: Int?) -> some View {
        switch item {
        case .step(let text):
            HStack(alignment: .firstTextBaseline, spacing: 6) {
                Text("\(ordinal ?? 0).")
                    .foregroundStyle(.secondary)
                    .monospacedDigit()
                Text(text)
            }
            .font(.callout)
        case .bullet(let text):
            HStack(alignment: .firstTextBaseline, spacing: 6) {
                Text("•")
                    .foregroundStyle(.secondary)
                Text(text)
            }
            .font(.callout)
        case .paragraph(let text):
            Text(text)
                .font(.callout)
        }
    }
}

/// The `Targets:` muscles as wrapping capsule chips.
private struct TargetChips: View {
    let targets: [String]

    var body: some View {
        FlowLayout(spacing: 6) {
            ForEach(targets, id: \.self) { target in
                Text(target)
                    .font(.caption)
                    .padding(.horizontal, 10)
                    .padding(.vertical, 4)
                    .background(Color.accentColor.opacity(0.12), in: Capsule())
                    .foregroundStyle(Color.accentColor)
            }
        }
    }
}

/// Minimal leading-aligned wrapping layout for the target chips.
private struct FlowLayout: Layout {
    var spacing: CGFloat = 6

    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) -> CGSize {
        let rows = layoutRows(maxWidth: proposal.width ?? .infinity, subviews: subviews)
        let height = rows.map(\.height).reduce(0, +) + spacing * CGFloat(max(0, rows.count - 1))
        return CGSize(width: proposal.width ?? rows.map(\.width).max() ?? 0, height: height)
    }

    func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout ()) {
        var y = bounds.minY
        var index = 0
        for row in layoutRows(maxWidth: bounds.width, subviews: subviews) {
            var x = bounds.minX
            for size in row.sizes {
                subviews[index].place(
                    at: CGPoint(x: x, y: y),
                    proposal: ProposedViewSize(size)
                )
                x += size.width + spacing
                index += 1
            }
            y += row.height + spacing
        }
    }

    private struct Row {
        var sizes: [CGSize] = []
        var width: CGFloat = 0
        var height: CGFloat = 0
    }

    private func layoutRows(maxWidth: CGFloat, subviews: Subviews) -> [Row] {
        var rows: [Row] = []
        var current = Row()
        for subview in subviews {
            let size = subview.sizeThatFits(.unspecified)
            let next = current.sizes.isEmpty ? size.width : current.width + spacing + size.width
            if next > maxWidth, !current.sizes.isEmpty {
                rows.append(current)
                current = Row()
            }
            current.sizes.append(size)
            current.width = current.sizes.isEmpty ? 0 : current.width + (current.sizes.count == 1 ? size.width : spacing + size.width)
            current.height = max(current.height, size.height)
        }
        if !current.sizes.isEmpty { rows.append(current) }
        return rows
    }
}