//
//  StatsView.swift
//  Keging
//
//  통계 — 하루·주간·월간, 꺾은선 그래프. 주간·월간은 달력 기준 ↔ 오늘 기준 롤링 전환.
//  첫 화면에서 아래로 스와이프해 열리고, 위로 스와이프하거나 X로 닫는다.
//

import SwiftUI
import Charts

enum StatScope: String, CaseIterable, Identifiable {
    case day, week, month
    var id: String { rawValue }

    var title: LocalizedStringKey {
        switch self {
        case .day: "하루"
        case .week: "주간"
        case .month: "월간"
        }
    }
}

enum StatRangeMode: String {
    case calendar, rolling
}

struct StatsView: View {
    @EnvironmentObject private var recordStore: RecordStore
    var onClose: () -> Void

    @State private var scope: StatScope = .day
    @State private var weekMode: StatRangeMode = .calendar
    @State private var monthMode: StatRangeMode = .calendar

    /// 주 시작 = 월요일
    private var calendar: Calendar {
        var c = Calendar.current
        c.firstWeekday = 2
        return c
    }

    var body: some View {
        ZStack {
            AppTheme.background.ignoresSafeArea()
            VStack(spacing: 12) {
                header
                Picker("기간", selection: $scope) {
                    ForEach(StatScope.allCases) { Text($0.title).tag($0) }
                }
                .pickerStyle(.segmented)
                .padding(.horizontal, 20)

                if scope != .day { rangeModePicker }

                ScrollView {
                    VStack(spacing: 14) {
                        summaryCard
                        chartCard
                        if scope == .day { sessionListCard }
                    }
                    .padding(.horizontal, 20)
                    .padding(.bottom, 24)
                }
            }
        }
        .gesture(
            DragGesture(minimumDistance: 40)
                .onEnded { value in
                    if value.translation.height > 70, abs(value.translation.width) < 100 { onClose() }
                }
        )
        .onAppear {
            #if DEBUG
            if let index = CommandLine.arguments.firstIndex(of: "-statsScope"),
               index + 1 < CommandLine.arguments.count,
               let argScope = StatScope.allCases.first(where: { String(describing: $0) == CommandLine.arguments[index + 1] }) {
                scope = argScope
            }
            if CommandLine.arguments.contains("-statsRolling") {
                weekMode = .rolling
                monthMode = .rolling
            }
            #endif
        }
    }

    // MARK: 헤더·피커

    private var header: some View {
        VStack(spacing: 6) {
            // 아래로 쓸어내려 닫기 손잡이
            Capsule()
                .fill(.secondary.opacity(0.5))
                .frame(width: 36, height: 5)
                .padding(.top, 8)
            HStack {
                Text("통계")
                    .font(.largeTitle.bold())
                Spacer()
                Button(action: onClose) {
                    Image(systemName: "xmark")
                        .font(.headline)
                        .foregroundStyle(.secondary)
                        .frame(width: 36, height: 36)
                        .background(AppTheme.surface, in: Circle())
                }
                .buttonStyle(.plain)
                .accessibilityLabel(Text("통계 닫기"))
            }
            .padding(.horizontal, 20)
        }
    }

    private var rangeModePicker: some View {
        Picker("범위", selection: scope == .week ? $weekMode : $monthMode) {
            Text(scope == .week ? "이번 주" : "이번 달").tag(StatRangeMode.calendar)
            Text(scope == .week ? "지난 7일" : "지난 30일").tag(StatRangeMode.rolling)
        }
        .pickerStyle(.segmented)
        .padding(.horizontal, 20)
    }

    // MARK: 데이터

    private struct DayCount: Identifiable {
        let date: Date
        let sets: Int
        let reps: Int
        var id: Date { date }
    }

    private struct HourCount: Identifiable {
        let hour: Int
        let reps: Int
        var id: Int { hour }
    }

    /// 현재 범위의 날짜(자정) 목록
    private var rangeDates: [Date] {
        let today = calendar.startOfDay(for: Date())
        switch scope {
        case .day:
            return [today]
        case .week:
            if weekMode == .rolling {
                return (0..<7).reversed().map { calendar.date(byAdding: .day, value: -$0, to: today)! }
            }
            let start = calendar.dateInterval(of: .weekOfYear, for: Date())!.start
            return (0..<7).map { calendar.date(byAdding: .day, value: $0, to: start)! }
        case .month:
            if monthMode == .rolling {
                return (0..<30).reversed().map { calendar.date(byAdding: .day, value: -$0, to: today)! }
            }
            let start = calendar.dateInterval(of: .month, for: Date())!.start
            let count = calendar.range(of: .day, in: .month, for: Date())!.count
            return (0..<count).map { calendar.date(byAdding: .day, value: $0, to: start)! }
        }
    }

    private func records(on day: Date) -> [SessionRecord] {
        recordStore.records.filter { calendar.startOfDay(for: $0.startedAt) == day }
    }

    private var dayCounts: [DayCount] {
        rangeDates.map { day in
            let dayRecords = records(on: day)
            return DayCount(date: day, sets: dayRecords.count, reps: dayRecords.reduce(0) { $0 + $1.reps })
        }
    }

    private var hourCounts: [HourCount] {
        let todayRecords = records(on: calendar.startOfDay(for: Date()))
        var byHour: [Int: Int] = [:]
        for record in todayRecords {
            let hour = calendar.component(.hour, from: record.startedAt)
            byHour[hour, default: 0] += record.reps
        }
        return (0..<24).map { HourCount(hour: $0, reps: byHour[$0] ?? 0) }
    }

    private var totalSets: Int { dayCounts.reduce(0) { $0 + $1.sets } }
    private var totalReps: Int { dayCounts.reduce(0) { $0 + $1.reps } }

    // MARK: 카드

    private var summaryCard: some View {
        HStack(spacing: 0) {
            summaryItem(value: "\(totalSets)", label: Text("세트"))
            Divider().frame(height: 36)
            summaryItem(value: "\(totalReps)", label: Text("횟수"))
        }
        .padding(.vertical, 16)
        .frame(maxWidth: .infinity)
        .background(AppTheme.surface, in: RoundedRectangle(cornerRadius: 16))
    }

    private func summaryItem(value: String, label: Text) -> some View {
        VStack(spacing: 4) {
            Text(value)
                .font(.title.bold())
                .monospacedDigit()
                .foregroundStyle(AppTheme.green)
            label
                .font(.caption)
                .foregroundStyle(.secondary)
        }
        .frame(maxWidth: .infinity)
    }

    private var chartCard: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text(scope == .day ? "시간대별 횟수" : "일별 횟수")
                .font(.headline)
            if totalSets == 0 {
                Text("이 기간에는 아직 기록이 없어요.")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                    .frame(maxWidth: .infinity, minHeight: 120)
            } else if scope == .day {
                dayChart
            } else {
                rangeChart
            }
        }
        .padding(16)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(AppTheme.surface, in: RoundedRectangle(cornerRadius: 16))
    }

    private var dayChart: some View {
        Chart(hourCounts) { item in
            LineMark(
                x: .value("시", item.hour),
                y: .value("횟수", item.reps)
            )
            .foregroundStyle(AppTheme.green)
            if item.reps > 0 {
                PointMark(
                    x: .value("시", item.hour),
                    y: .value("횟수", item.reps)
                )
                .foregroundStyle(AppTheme.green)
            }
        }
        .chartXScale(domain: 0...23)
        .chartXAxis {
            AxisMarks(values: [0, 6, 12, 18, 23]) { value in
                AxisGridLine()
                AxisValueLabel {
                    if let hour = value.as(Int.self) { Text("\(hour)시") }
                }
            }
        }
        .frame(height: 200)
    }

    private var rangeChart: some View {
        Chart(dayCounts) { item in
            LineMark(
                x: .value("날짜", item.date, unit: .day),
                y: .value("횟수", item.reps)
            )
            .foregroundStyle(AppTheme.green)
            PointMark(
                x: .value("날짜", item.date, unit: .day),
                y: .value("횟수", item.reps)
            )
            .foregroundStyle(AppTheme.green)
        }
        .chartXAxis {
            if scope == .week {
                AxisMarks(values: .stride(by: .day)) { _ in
                    AxisGridLine()
                    AxisValueLabel(format: .dateTime.weekday(.narrow), centered: true)
                }
            } else {
                AxisMarks(values: .automatic(desiredCount: 6)) { _ in
                    AxisGridLine()
                    AxisValueLabel(format: .dateTime.day(), centered: true)
                }
            }
        }
        .frame(height: 200)
    }

    private var sessionListCard: some View {
        VStack(alignment: .leading, spacing: 12) {
            Text("오늘 기록")
                .font(.headline)
            let todayRecords = records(on: calendar.startOfDay(for: Date()))
            if todayRecords.isEmpty {
                Text("오늘은 아직 기록이 없어요.")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
            } else {
                ForEach(todayRecords.sorted { $0.startedAt > $1.startedAt }) { record in
                    HStack {
                        Text(record.startedAt, format: .dateTime.hour().minute())
                            .font(.body)
                        Spacer()
                        Text("\(record.reps)회")
                            .font(.body.weight(.semibold))
                            .monospacedDigit()
                            .foregroundStyle(AppTheme.green)
                    }
                    .padding(.vertical, 2)
                }
            }
        }
        .padding(16)
        .frame(maxWidth: .infinity, alignment: .leading)
        .background(AppTheme.surface, in: RoundedRectangle(cornerRadius: 16))
    }
}