//
//  AdminQueueView.swift
//  FTStore Admin
//
//  What the scraper has found and what it is doing with it. This is where
//  someone looks when downloads stop moving, so the storage cap gets its own
//  banner exactly like the web page.
//

import SwiftUI

struct AdminQueueView: View {
	@EnvironmentObject private var session: AdminSession

	@StateObject private var _queue = AdminLoader<AdminQueueResponse>()

	@State private var _status: String?
	@State private var _search = ""
	@State private var _page = 1
	@State private var _busyIds: Set<Int> = []
	@State private var _banner: String?

	private static let _statuses = [
		"pending", "downloading", "processing", "completed", "failed", "skipped",
	]

	var body: some View {
		List {
			_storageBanner
			_statsSection

			if let banner = _banner {
				Section {
					Text(banner).font(.footnote).foregroundStyle(.secondary)
				}
			}

			_itemsSection
			_pagingSection
			_bulkSection
		}
		.navigationTitle("Queue")
		.navigationBarTitleDisplayMode(.inline)
		.searchable(text: $_search, prompt: "File name")
		.refreshable { await _reload() }
		.task { await _reload() }
		.onChange(of: _search) { _ in
			_page = 1
			Task { await _reload() }
		}
		.onChange(of: _status) { _ in
			_page = 1
			Task { await _reload() }
		}
		.toolbar {
			ToolbarItem(placement: .topBarTrailing) {
				Menu {
					Picker("Status", selection: $_status) {
						Text("All").tag(String?.none)
						ForEach(Self._statuses, id: \.self) { status in
							Text(status.capitalized).tag(String?.some(status))
						}
					}
				} label: {
					Image(systemName: _status == nil
						? "line.3.horizontal.decrease.circle"
						: "line.3.horizontal.decrease.circle.fill")
				}
			}
		}
	}

	// MARK: Sections

	@ViewBuilder
	private var _storageBanner: some View {
		if let storage = _queue.value?.storage, storage.blocked {
			Section {
				Label(
					"Storage is full (\(AdminFormat.bytes(storage.usedBytes)) of \(AdminFormat.bytes(storage.limitBytes))). Downloads stay pending until space frees up.",
					systemImage: "externaldrive.badge.exclamationmark"
				)
				.font(.footnote)
				.foregroundStyle(.red)
			}
		}
	}

	@ViewBuilder
	private var _statsSection: some View {
		if let stats = _queue.value?.stats {
			Section {
				LazyVGrid(
					columns: [GridItem(.flexible(), spacing: 8), GridItem(.flexible(), spacing: 8), GridItem(.flexible(), spacing: 8)],
					spacing: 8
				) {
					_stat("Pending", stats.pending, .orange)
					_stat("Active", stats.active, AdminTheme.brand)
					_stat("Done", stats.completed, .green)
					_stat("Failed", stats.failed, .red)
					_stat("Skipped", stats.skipped, .secondary)
					_stat("Total", stats.pending + stats.active + stats.completed + stats.failed + stats.skipped, .primary)
				}
				.listRowInsets(EdgeInsets(top: 8, leading: 12, bottom: 8, trailing: 12))
				.listRowBackground(Color.clear)
			}
		}
	}

	private func _stat(_ title: String, _ value: Int, _ tint: Color) -> some View {
		VStack(spacing: 2) {
			Text(AdminFormat.count(value))
				.font(.headline.monospacedDigit())
				.foregroundStyle(tint)
			Text(title)
				.font(.caption2)
				.foregroundStyle(.secondary)
		}
		.frame(maxWidth: .infinity)
		.padding(.vertical, 8)
		.background(
			Color(uiColor: .secondarySystemBackground),
			in: RoundedRectangle(cornerRadius: 12, style: .continuous)
		)
	}

	@ViewBuilder
	private var _itemsSection: some View {
		Section {
			if _queue.isLoading {
				AdminLoadingRow()
			} else if let error = _queue.errorMessage, !_queue.hasLoaded {
				AdminErrorRow(message: error) { Task { await _reload() } }
			} else if let items = _queue.value?.data, items.isEmpty {
				AdminEmptyRow(icon: "tray", title: "Queue is empty")
			} else if let items = _queue.value?.data {
				ForEach(items) { item in
					_row(item)
						.swipeActions(edge: .trailing) {
							if item.status == "failed" {
								Button {
									_retry(item)
								} label: {
									Label("Retry", systemImage: "arrow.clockwise")
								}
								.tint(AdminTheme.brand)
							}
							Button(role: .destructive) {
								_batch("delete", ids: [item.id])
							} label: {
								Label("Delete", systemImage: "trash")
							}
							Button {
								_batch("skip", ids: [item.id])
							} label: {
								Label("Skip", systemImage: "forward.end")
							}
							.tint(.orange)
						}
				}
			}
		} header: {
			if let total = _queue.value?.total {
				Text(
				total == 1
					? String.localized("1 item")
					: String.localized("%@ items", AdminFormat.count(total))
			)
			}
		}
	}

	private func _row(_ item: AdminQueueItem) -> some View {
		VStack(alignment: .leading, spacing: 4) {
			Text(item.fileName ?? "Message \(item.messageId)")
				.font(.subheadline)
				.lineLimit(2)
			HStack(spacing: 8) {
				AdminStatusPill(status: item.status)
				if let size = item.fileSize {
					Text(AdminFormat.bytes(size))
						.font(.caption)
						.foregroundStyle(.secondary)
				}
				Text(_channelName(item.channelId))
					.font(.caption2)
					.foregroundStyle(.tertiary)
					.lineLimit(1)
				Spacer()
				if _busyIds.contains(item.id) {
					ProgressView()
				} else {
					Text(AdminFormat.relative(item.updatedAt))
						.font(.caption2)
						.foregroundStyle(.tertiary)
				}
			}
			if let error = item.error, !error.isEmpty {
				Text(error)
					.font(.caption2)
					.foregroundStyle(.red)
					.lineLimit(2)
			}
		}
		.padding(.vertical, 2)
	}

	@ViewBuilder
	private var _pagingSection: some View {
		if let response = _queue.value, response.totalPages > 1 {
			Section {
				HStack {
					Button("Previous") {
						_page = max(1, _page - 1)
						Task { await _reload() }
					}
					.disabled(_page <= 1)

					Spacer()
					Text("Page \(response.page) of \(response.totalPages)")
						.font(.caption)
						.foregroundStyle(.secondary)
					Spacer()

					Button("Next") {
						_page = min(response.totalPages, _page + 1)
						Task { await _reload() }
					}
					.disabled(_page >= response.totalPages)
				}
				.font(.subheadline)
			}
		}
	}

	@ViewBuilder
	private var _bulkSection: some View {
		if let stats = _queue.value?.stats {
			Section("Bulk") {
				AdminActionRow(
					title: "Retry All Failed",
					icon: "arrow.clockwise",
					detail: stats.failed == 1
						? .localized("1 failed item")
						: .localized("%lld failed items", stats.failed)
				) {
					let ack = try await session.act(
						.post,
						"/api/queue/retry",
						body: AdminRequest.RetryAll(all: true)
					)
					await _reload()
					return ack.summary
				}
				.disabled(stats.failed == 0)

				AdminActionRow(
					title: "Clear Completed",
					icon: "trash",
					detail: stats.completed == 1
						? .localized("1 completed item")
						: .localized("%lld completed items", stats.completed),
					destructive: true,
					confirmation: "Delete every completed queue entry?"
				) {
					let ack = try await session.act(
						.post,
						"/api/queue/batch",
						body: AdminRequest.QueueBatch(action: "delete", status: "completed")
					)
					await _reload()
					return ack.summary
				}
				.disabled(stats.completed == 0)
			}
		}
	}

	// MARK: Helpers

	private func _channelName(_ id: String) -> String {
		_queue.value?.channelNames?[id] ?? id
	}

	private func _reload() async {
		var query = ["page": String(_page), "pageSize": "50"]
		if let _status { query["status"] = _status }
		let needle = _search.trimmingCharacters(in: .whitespaces)
		if !needle.isEmpty { query["search"] = needle }

		await _queue.load {
			try await session.get("/api/queue", query: query, as: AdminQueueResponse.self)
		}
	}

	private func _retry(_ item: AdminQueueItem) {
		_run(item.id) {
			try await session.act(
				.post,
				"/api/queue/retry",
				body: AdminRequest.Identified(id: item.id)
			).summary
		}
	}

	private func _batch(_ action: String, ids: [Int]) {
		_run(ids.first ?? 0) {
			try await session.act(
				.post,
				"/api/queue/batch",
				body: AdminRequest.QueueBatch(action: action, ids: ids)
			).summary
		}
	}

	private func _run(_ id: Int, _ operation: @escaping @MainActor () async throws -> String) {
		_busyIds.insert(id)
		Task { @MainActor in
			do {
				_banner = try await operation()
			} catch {
				_banner = (error as? LocalizedError)?.errorDescription ?? error.localizedDescription
			}
			_busyIds.remove(id)
			await _reload()
		}
	}
}