//

//  ChargedDeviceSessionsView.swift

//  USB Meter

//

//  Created by Codex on 22/04/2026.

//

import SwiftUI

struct ChargedDeviceSessionsView: View {

    @EnvironmentObject private var appData: AppData

    @State private var pendingSessionDeletion: ChargeSessionSummary?

    let chargedDeviceID: UUID

    private var chargedDevice: ChargedDeviceSummary? {

        appData.chargedDeviceSummary(id: chargedDeviceID)

    }

    private var sessions: [ChargeSessionSummary] {

        chargedDevice?.sessions.filter { !$0.status.isOpen } ?? []

    }

    private var capacityDeltas: [UUID: Double] {

        let sorted = sessions.sorted { $0.startedAt < $1.startedAt }

        var result: [UUID: Double] = [:]

        var previousCapacity: Double? = nil

        for session in sorted {

            if let current = session.capacityEstimateWh {

                if let prev = previousCapacity {

                    result[session.id] = current - prev

                }

                previousCapacity = current

            }

        }

        return result

    }

        Group {

            if let chargedDevice {

                ScrollView {

                    VStack(spacing: 14) {

                        if sessions.isEmpty {

                            emptyState

                        } else {

                            summaryHeader(chargedDevice)

                        }

                    }

                    .padding()

                }

                .background(

                    LinearGradient(

                        colors: [tint(for: chargedDevice).opacity(0.14), Color.clear],

                        startPoint: .topLeading,

                        endPoint: .bottomTrailing

                    )

                    .ignoresSafeArea()

                )

                .navigationTitle("Sessions")

                Text("This device is no longer available.")

                    .foregroundColor(.secondary)

                    .navigationTitle("Sessions")

        }

        .alert(item: $pendingSessionDeletion) { session in

            Alert(

                title: Text("Delete Session?"),

                message: Text("Deleting this charging session also recalculates capacity and every derived metric that used it."),

                primaryButton: .destructive(Text("Delete")) {

                    _ = appData.deleteChargeSession(sessionID: session.id)

                },

                secondaryButton: .cancel()

            )

        }

    }

    private var emptyState: some View {

        VStack(spacing: 10) {

            Image(systemName: "clock")

                .font(.system(size: 34, weight: .semibold))

                .foregroundColor(.secondary)

            Text("No Closed Sessions")

                .font(.headline)

            Text("Completed and abandoned sessions will appear here after they are closed.")

                .font(.footnote)

                .foregroundColor(.secondary)

                .multilineTextAlignment(.center)

        }

        .frame(maxWidth: .infinity)

        .padding(24)

        .meterCard(tint: .secondary, fillOpacity: 0.10, strokeOpacity: 0.14, cornerRadius: 18)

    }

    private func summaryHeader(_ chargedDevice: ChargedDeviceSummary) -> some View {

        let totalEnergyWh = sessions.reduce(0) { $0 + $1.effectiveOrMeasuredEnergyWh }

        let completedCount = sessions.filter { $0.status == .completed }.count

        return MeterInfoCardView(title: chargedDevice.name, tint: tint(for: chargedDevice)) {

            MeterInfoRowView(label: "Closed Sessions", value: "\(sessions.count)")

            MeterInfoRowView(label: "Completed", value: "\(completedCount)")

            MeterInfoRowView(label: "Total Energy", value: "\(totalEnergyWh.format(decimalDigits: 2)) Wh")

        }

    }

    private func sessionCard(

        _ session: ChargeSessionSummary,

        chargedDevice: ChargedDeviceSummary,

        capacityDelta: Double?

    ) -> some View {

        let sessionTint = statusTint(for: session)

        return VStack(alignment: .leading, spacing: 10) {

                    sessionID: session.id

                )

            ) {

                VStack(alignment: .leading, spacing: 10) {

                        Text(session.startedAt.format())

                            .font(.subheadline.weight(.semibold))

                            .foregroundColor(.primary)

                        Text(session.status.title)

                            .font(.caption2.weight(.semibold))

                            .padding(.vertical, 4)

                            Image(systemName: "exclamationmark.arrow.trianglehead.2.clockwise.rotate.90")

                                .font(.caption2.weight(.semibold))

                                .foregroundColor(.orange)

                                .help("This session was automatically closed because a newer session was started on another device while offline.")

                        }

                        Image(systemName: "chevron.right")

                            .font(.caption.weight(.semibold))

                            .foregroundColor(.secondary)

                    }

                    HStack(spacing: 8) {

                        primaryMetricCell(

                            label: "Energy",

                            value: "\(session.effectiveOrMeasuredEnergyWh.format(decimalDigits: 2)) Wh",

                            tint: .teal

                        )

                        primaryMetricCell(

                            label: "Duration",

                            value: sessionDurationText(session),

                            tint: .orange

                        )

                    }

                    if let chargeRange = chargeBarRange(for: session) {

                        chargeBarView(range: chargeRange, tint: sessionTint)

                    }

                    // Capacity estimate + battery delta chips

                    let chips = chipContent(session: session, capacityDelta: capacityDelta)

                    if !chips.isEmpty {

                        chipsRow(chips)

                    }

                    // Secondary info line

                    let secondary = secondaryInfoLine(session, chargedDevice: chargedDevice)

                    if !secondary.isEmpty {

                        Text(secondary)

                            .font(.caption)

                            .foregroundColor(.secondary)

                }

            }

            .buttonStyle(.plain)

            Divider()

            HStack {

                if !session.displayedAggregatedSamples.isEmpty {

                    Label("\(session.displayedAggregatedSamples.count) curve points", systemImage: "chart.xyaxis.line")

                        .font(.caption2)

                        .foregroundColor(.secondary)

                }

                Spacer()

                Button(role: .destructive) {

                    pendingSessionDeletion = session

                } label: {

                    Image(systemName: "trash")

                        .font(.caption.weight(.semibold))

                        .foregroundColor(.red)

                        .frame(width: 30, height: 30)

                .buttonStyle(.plain)

                .help("Delete session")

            }

        }

        .padding(14)

        VStack(alignment: .leading, spacing: 3) {

                .font(.caption2)

                .foregroundColor(.secondary)

            Text(value)

                .monospacedDigit()

                .lineLimit(1)

                .minimumScaleFactor(0.8)

        }

        .frame(maxWidth: .infinity, alignment: .leading)

        .padding(10)

        .meterCard(tint: tint, fillOpacity: 0.08, strokeOpacity: 0.12, cornerRadius: 12)

    }

    /// Returns (startPercent, endPercent) if we have enough data to render a charge bar.

    private func chargeBarRange(for session: ChargeSessionSummary) -> (start: Double, end: Double)? {

        let start = session.startBatteryPercent

        let end = session.endBatteryPercent

        if let s = start, let e = end, e > s {

            return (s, e)

        }

        // Fall back to first / last checkpoint

        let sorted = session.checkpoints.sorted { $0.timestamp < $1.timestamp }

        if sorted.count >= 2,

           let first = sorted.first,

           let last = sorted.last,

           last.batteryPercent > first.batteryPercent {

            return (first.batteryPercent, last.batteryPercent)

        }

        return nil

    }

    private func chargeBarView(range: (start: Double, end: Double), tint: Color) -> some View {

        VStack(alignment: .leading, spacing: 4) {

            GeometryReader { geo in

                let w = geo.size.width

                let startX = w * CGFloat(range.start / 100)

                let fillWidth = max(w * CGFloat((range.end - range.start) / 100), 4)

                ZStack(alignment: .leading) {

                    Capsule()

                        .fill(Color.primary.opacity(0.08))

                    // Filled charged portion

                    Rectangle()

                        .fill(LinearGradient(

                            colors: [tint.opacity(0.6), tint],

                            startPoint: .leading,

                            endPoint: .trailing

                        ))

                        .frame(width: fillWidth)

                        .offset(x: startX)

                    // Start marker line

                    if range.start > 3 {

                        Rectangle()

                            .fill(Color.white.opacity(0.5))

                            .frame(width: 1.5, height: 14)

                            .offset(x: startX - 0.75)

                    }

                }

                .clipShape(Capsule())

            }

            .frame(height: 14)

            // Labels

            HStack {

                Text("\(Int(range.start.rounded()))%")

                    .font(.caption2)

                    .foregroundColor(.secondary)

                Spacer()

                Text("+\(Int((range.end - range.start).rounded()))%")

                    .font(.caption2.weight(.semibold))

                    .foregroundColor(tint)

                Spacer()

                Text("\(Int(range.end.rounded()))%")

                    .font(.caption2)

                    .foregroundColor(.secondary)

            }

        }

    }

    // MARK: - Chips

    private struct ChipContent {

        let label: String

        let tint: Color

    }

    private func chipContent(session: ChargeSessionSummary, capacityDelta: Double?) -> [ChipContent] {

        var chips: [ChipContent] = []

        if let capacityWh = session.capacityEstimateWh {

            var label = "\(capacityWh.format(decimalDigits: 1)) Wh"

            if let delta = capacityDelta {

                let sign = delta >= 0 ? "+" : ""

                label += " (\(sign)\(delta.format(decimalDigits: 1)))"

            }

            chips.append(ChipContent(label: label, tint: .orange))

        }

        if let batteryDelta = session.batteryDeltaPercent {

            let sign = batteryDelta >= 0 ? "+" : ""

            chips.append(ChipContent(label: "\(sign)\(Int(batteryDelta.rounded()))% charged", tint: .teal))

        }

        return chips

    }

    private func chipsRow(_ chips: [ChipContent]) -> some View {

        HStack(spacing: 6) {

            ForEach(chips.indices, id: \.self) { i in

                let chip = chips[i]

                Text(chip.label)

                    .font(.caption2.weight(.semibold))

                    .foregroundColor(chip.tint)

                    .padding(.horizontal, 8)

                    .padding(.vertical, 4)

                    .background(

                        RoundedRectangle(cornerRadius: 8)

                            .fill(chip.tint.opacity(0.14))

                            .overlay(RoundedRectangle(cornerRadius: 8).stroke(chip.tint.opacity(0.22), lineWidth: 1))

                    )

            }

            Spacer()

        }

    }

    // MARK: - Secondary info line

    private func secondaryInfoLine(

        chargedDevice: ChargedDeviceSummary

    ) -> String {

        var components: [String] = []

        if chargedDevice.shouldShowChargingTransport(session.chargingTransportMode) {

            components.append(session.chargingTransportMode.title)

        }

        if chargedDevice.shouldShowChargingStateMode(session.chargingStateMode) {

            components.append(session.chargingStateMode.title)

        }

        if session.isTrimmed {

            components.append("Trimmed")

        }

            components.append("Auto-closed (sync conflict)")

        }

        let formatter = DateComponentsFormatter()

        let effectiveDuration = max(session.effectiveDuration, 0)

        formatter.allowedUnits = effectiveDuration >= 3600 ? [.hour, .minute] : [.minute, .second]

        formatter.unitsStyle = .abbreviated

        formatter.zeroFormattingBehavior = .dropAll

        return formatter.string(from: effectiveDuration) ?? "0m"

    }

    private func statusTint(for session: ChargeSessionSummary) -> Color {

        switch session.status {

        case .paused:   return .orange

        case .completed: return .teal

        case .abandoned: return .secondary

    }

    private func tint(for chargedDevice: ChargedDeviceSummary) -> Color {

        switch chargedDevice.deviceClass {

        case .watch:     return .green

        case .powerbank: return .orange

        case .charger:   return .pink

        case .other:     return .secondary

    }

}