//
//  AdminTweakRequestsView.swift
//  FTStore Admin
//
//  Mirrors /admin/tweak-requests: the sources people asked FTStore to follow,
//  folded together and ranked by how many asked.
//
//  A row is a *source*, not a single request, because that is what a decision
//  acts on. Answering one clears every open request for it, with the same reason
//  going to everyone who asked.
//
//  A decision is approve or reject and nothing else. Approving used to be able
//  to create the scraper source in the same step; adding a source is now its own
//  deliberate action in Channels & Sources.
//
//  Whatever is typed into the reason field is shown to the requesters in the
//  FTStore app, so it is written for them. It is optional either way.
//

import SwiftUI

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

	@StateObject private var _requests = AdminLoader<AdminEnvelope<[AdminTweakRequest]>>()

	/// Busy state is keyed by `groupKey` — the row's identity. Not `sourceId`,
	/// which is null for a wish nobody named a source for.
	@State private var _busyIds: Set<String> = []
	@State private var _banner: String?

	/// The group waiting on a "really?", if any.
	@State private var _removing: AdminTweakRequest?

	/// The group the reason prompt is about, and what it will do.
	@State private var _deciding: AdminTweakRequest?
	@State private var _decidingApproval = false
	@State private var _reason = ""

	/// Filters the loaded queue in place. The server takes a `search` parameter
	/// too, but the grouped response is already the whole ranked queue, so
	/// matching here keeps typing instant and the demand ranking intact.
	@State private var _search = ""

	private var _all: [AdminTweakRequest] {
		let rows = _requests.value?.data ?? []
		let query = _search.trimmingCharacters(in: .whitespacesAndNewlines)
		guard !query.isEmpty else { return rows }
		return rows.filter { $0.matches(query) }
	}

	private var _pending: [AdminTweakRequest] { _all.filter(\.isPending) }
	private var _decided: [AdminTweakRequest] { _all.filter { !$0.isPending } }

	var body: some View {
		List {
			if let banner = _banner {
				Section {
					Text(banner).font(.footnote).foregroundStyle(.secondary)
				}
			}

			if _requests.isLoading {
				AdminLoadingRow()
			} else if let error = _requests.errorMessage, !_requests.hasLoaded {
				AdminErrorRow(message: error) { Task { await _reload() } }
			} else if _all.isEmpty {
				if _search.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty {
					AdminEmptyRow(
						icon: "tray",
						title: "No requests",
						detail: "Sources people ask for from the FTStore app land here, most wanted first."
					)
				} else {
					AdminEmptyRow(
						icon: "magnifyingglass",
						title: "No matches",
						detail: "Nothing in the queue matches that tweak name or source."
					)
				}
			} else {
				if !_pending.isEmpty {
					Section {
						ForEach(_pending) { group in
							_link(group)
						}
					} header: {
						Text("Waiting for review")
					} footer: {
						Text("Most wanted first. Deciding a source answers everyone who asked for it.")
					}
				}

				if !_decided.isEmpty {
					Section("Decided") {
						ForEach(_decided) { group in
							_link(group)
						}
					}
				}
			}
		}
		.navigationTitle("Tweak Requests")
		.navigationBarTitleDisplayMode(.inline)
		.searchable(text: $_search, prompt: "Search tweak or source")
		.autocorrectionDisabled()
		.textInputAutocapitalization(.never)
		.refreshable { await _reload() }
		.task { await _reload() }
		.alert("Delete this request for good?", isPresented: _isRemoving) {
			Button("Delete", role: .destructive) { _commitDelete() }
			Button("Cancel", role: .cancel) { _removing = nil }
		} message: {
			if let group = _removing {
				Text(verbatim: _deleteMessage(for: group))
			}
		}
		.alert(_decidingApproval ? "Approve request" : "Reject request", isPresented: _isDeciding) {
			TextField("Reason (optional)", text: $_reason)
			let role: ButtonRole? = _decidingApproval ? nil : .destructive
			Button(_decidingApproval ? "Approve" : "Reject", role: role) {
				_commitDecision()
			}
			Button("Cancel", role: .cancel) { _deciding = nil }
		} message: {
			if let group = _deciding {
				Text(_promptMessage(for: group))
			}
		}
	}

	/// The alert is bound to "is a group selected", so dismissing it any way
	/// clears the selection rather than leaving a stale target behind.
	private var _isDeciding: Binding<Bool> {
		Binding(
			get: { _deciding != nil },
			set: { if !$0 { _deciding = nil } }
		)
	}

	private var _isRemoving: Binding<Bool> {
		Binding(
			get: { _removing != nil },
			set: { if !$0 { _removing = nil } }
		)
	}

	/// The part an operator is not thinking about: the replies belong to
	/// whoever wrote them, and this takes those too.
	private func _deleteMessage(for group: AdminTweakRequest) -> String {
		var lines = ["\(group.tweakName) · \(group.sourceLabelOrNone)"]
		let replies = group.commentCount ?? 0
		if replies > 0 {
			// Two strings rather than one with a plural variation, which is the
			// idiom the rest of this app already uses for a count.
			lines.append(
				replies == 1
					? String.localized("The one reply written under it goes too.")
					: String.localized("The %lld replies written under it go too.", replies)
			)
		}
		lines.append(.localized("Rejecting it is the reversible option."))
		return lines.joined(separator: " ")
	}

	private func _promptMessage(for group: AdminTweakRequest) -> String {
		var lines = ["\(group.tweakName) · \(group.sourceLabelOrNone)"]
		if group.pendingIds.count > 1 {
			lines.append("This answers all \(group.pendingIds.count) open requests for that source.")
		}
		lines.append("The reason is shown to everyone who asked.")
		return lines.joined(separator: " ")
	}

	// MARK: Row

	/// The row, and the way into the conversation under it.
	///
	/// A plain `NavigationLink` rather than an entry in a menu. Reading what
	/// people said is the common thing to do with a request and deciding it is
	/// the rare one, so the common thing is the tap and the rare one is a swipe.
	/// It also matches the feedback queue in this app, where tapping a row has
	/// always opened the thread.
	@ViewBuilder
	private func _link(_ group: AdminTweakRequest) -> some View {
		Group {
			if let threadId = group.threadId {
				NavigationLink {
					AdminTweakRequestThreadView(group: group, requestId: threadId) {
						await _reload()
					}
					.environmentObject(session)
				} label: {
					_row(group)
				}
			} else {
				// A settled group on a server that predates `boardId`. Nothing
				// to open, so the row does not pretend there is.
				_row(group)
			}
		}
		// On the row the List lays out rather than inside the link's label,
		// which is where a swipe would never reach them.
		.swipeActions(edge: .trailing) {
			if group.isPending {
				Button("Reject", role: .destructive) { _prompt(group, approve: false) }
			}
		}
		.swipeActions(edge: .leading) {
			if group.isPending {
				Button("Approve") { _prompt(group, approve: true) }
					.tint(.green)
			}
		}
		.contextMenu {
			// Behind a long press rather than on the trailing edge with Reject:
			// rejecting is the reversible answer and should be the one under a
			// thumb. This destroys other people's replies too.
			Button(role: .destructive) {
				_removing = group
			} label: {
				Label("Delete", systemImage: "trash")
			}
		}
	}

	private func _row(_ group: AdminTweakRequest) -> some View {
		HStack(alignment: .top, spacing: 12) {
			// The demand count is the point of the grouped list, so it leads.
			VStack(spacing: 1) {
				Text(verbatim: "\(group.requestCount)")
					.font(.headline.monospacedDigit())
					.foregroundStyle(AdminTheme.brand)
				Group {
					if group.sourceType == "github" {
						Image(systemName: "chevron.left.forwardslash.chevron.right")
					} else {
						TelegramMark(size: 10)
					}
				}
				.font(.caption2)
				.foregroundStyle(.tertiary)
			}
			.frame(width: 30)

			VStack(alignment: .leading, spacing: 3) {
				HStack(alignment: .firstTextBaseline, spacing: 5) {
					if group.isPinned {
						Image(systemName: "pin.fill")
							.font(.caption2)
							.foregroundStyle(AdminTheme.brand)
					}
					Text(group.tweakName)
						.font(.subheadline.weight(.medium))
				}

				Text(group.sourceLabelOrNone)
					.font(.caption)
					.foregroundStyle(.secondary)

				if !group.otherNames.isEmpty {
					Text(String.localized(
						"also: %@",
						group.otherNames.map { "\($0.name) (\($0.count))" }.joined(separator: ", ")
					))
						.font(.caption2)
						.foregroundStyle(.tertiary)
						.lineLimit(2)
				}

				if let note = group.note, !note.isEmpty {
					Text(note)
						.font(.caption2)
						.foregroundStyle(.tertiary)
						.lineLimit(2)
				}

				if let asked = group.lastRequestedAt {
					Text("last asked \(AdminFormat.relative(asked))")
						.font(.caption2)
						.foregroundStyle(.tertiary)
				}

				// What the app's users did with this wish, which is a different
				// number from the demand count on the left: that counts the
				// people who asked before there was anywhere to say "me too",
				// this counts the ones who said it.
				HStack(spacing: 8) {
					Label(group.votes.scoreLabel, systemImage: "arrowtriangle.up")
					Label("\(group.commentCount ?? 0)", systemImage: "bubble.left")
				}
				.font(.caption2.monospacedDigit())
				.foregroundStyle(.tertiary)

				if let reason = group.decisionReason, !reason.isEmpty {
					Text(reason)
						.font(.caption2)
						.foregroundStyle(.secondary)
				}
			}

			Spacer(minLength: 0)

			if _busyIds.contains(group.groupKey) {
				ProgressView()
			} else if !group.isPending {
				AdminStatusPill(status: group.status)
			}
		}
		.padding(.vertical, 2)
	}

	// MARK: Actions

	private func _reload() async {
		await _requests.load {
			try await session.get("/api/tweak-requests", as: AdminEnvelope<[AdminTweakRequest]>.self)
		}
	}

	private func _prompt(_ group: AdminTweakRequest, approve: Bool) {
		_reason = ""
		_decidingApproval = approve
		_deciding = group
	}

	private func _commitDecision() {
		guard let group = _deciding else { return }
		let approve = _decidingApproval
		let reason = _reason.trimmingCharacters(in: .whitespacesAndNewlines)
		_deciding = nil

		_run(group.groupKey) {
			let ack = try await session.act(
				.put,
				"/api/tweak-requests",
				body: AdminRequest.TweakRequestDecision(
					ids: group.pendingIds,
					status: approve ? "approved" : "rejected",
					reason: reason.isEmpty ? nil : reason
				)
			)
			return ack.message ?? "\(group.tweakName) \(approve ? "approved" : "rejected")."
		}
	}

	private func _commitDelete() {
		guard let group = _removing else { return }
		_removing = nil

		_run(group.groupKey) {
			let ack = try await session.act(
				.delete,
				"/api/tweak-requests",
				// By row ids: a wish with no source cannot be named by one.
				body: AdminRequest.TweakRequestDelete(ids: group.allIds)
			)
			return ack.message ?? .localized("Request deleted.")
		}
	}

	private func _run(_ id: String, _ 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()
		}
	}
}