//
//  AdminServerSettingsView.swift
//  FTStore Admin
//
//  FTStore Admin's own settings, edited from the phone. `/api/settings` is a
//  flat key/value store, so this screen is driven by a descriptor table rather
//  than a hand-written form — a new server setting only needs a row here.
//
//  Credentials are deliberately read-only: the server already replaces
//  `github_token` and `ftstore_app_github_token` with a mask before serialising,
//  and Telegram's API hash is only ever entered in the web dashboard. This app
//  can see *that* a secret is configured, never what it is.
//
//  There is no Save button. A switch writes the moment it moves, and a text
//  field writes when it stops being edited — which is the point at which the
//  value is finished rather than half-typed. Every write carries the one key
//  that changed, so leaving a field alone can no longer send a stale copy of it
//  back over somebody else's change, which the old whole-form PUT did on every
//  press.
//

import SwiftUI

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

	@StateObject private var _settings = AdminLoader<AdminSettingsResponse>()

	@State private var _text: [String: String] = [:]
	@State private var _flags: [String: Bool] = [:]
	@State private var _saving = false
	@State private var _banner: String?

	/// What the server last told us each field holds.
	///
	/// Kept beside the editable copy so a field can be compared against it and
	/// skipped when nothing actually changed — tapping through a form should not
	/// write every value it passed.
	@State private var _savedText: [String: String] = [:]
	@State private var _savedFlags: [String: Bool] = [:]

	/// Which text field is being typed in. A field commits when this moves off
	/// it, which is the moment the value is finished rather than half-typed:
	/// saving per keystroke would send "ftstore.a" on the way to "ftstore.app".
	@FocusState private var _focused: String?

	// MARK: Descriptors

	private struct Field: Identifiable {
		enum Kind { case text, number, toggle }

		let key: String
		let title: String
		let kind: Kind
		var placeholder: String = ""

		var id: String { key }
	}

	private struct FieldGroup: Identifiable {
		let title: String
		let footer: String?
		let fields: [Field]

		var id: String { title }
	}

	// Two groups that used to be here are gone, and neither is coming back:
	//
	//  • "Source Metadata" (the `source_*` branding). FTStore is the only thing
	//    this server publishes, so its name, subtitle, description and tint are
	//    constants. Site domain stays below: it is deployment plumbing.
	//  • "Feed & Storage", whose one switch let an operator stop requiring the
	//    FTStore User-Agent on IPA downloads. Downloads are restricted to
	//    FTStore full stop now, so the switch is gone and its neighbours moved
	//    into the groups they belong in.
	private static let _groups: [FieldGroup] = [
		FieldGroup(
			title: "Server",
			footer: "The site domain is used for download links when the reverse proxy doesn't forward the original host. Leave it blank to derive it per request.",
			fields: [
				Field(key: "site_domain", title: "Site domain", kind: .text, placeholder: "ftstore.app"),
				Field(key: "appstore_country", title: "App Store country", kind: .text, placeholder: "us"),
			]
		),
		FieldGroup(
			title: "Intervals",
			footer: nil,
			fields: [
				Field(key: "scan_interval_minutes", title: "Scan every (min)", kind: .number),
				Field(key: "json_regen_interval_minutes", title: "Publish every (min)", kind: .number),
				Field(key: "cleanup_interval_hours", title: "Cleanup every (h)", kind: .number),
			]
		),
		FieldGroup(
			title: "Limits",
			footer: nil,
			fields: [
				Field(key: "max_versions_per_app", title: "Versions per app", kind: .number),
				Field(key: "log_retention_days", title: "Keep logs (days)", kind: .number),
				Field(key: "scan_message_limit", title: "Messages per scan", kind: .number),
				Field(key: "github_release_scan_limit", title: "GitHub releases per scan", kind: .number),
				Field(key: "previous_ipa_scan_amount", title: "Scan-previous depth", kind: .number),
			]
		),
		FieldGroup(
			title: "Storage",
			footer: "Max storage is in GiB; 0 means unlimited. When the cap is reached the scraper stops downloading, and manual uploads keep working.",
			fields: [
				Field(key: "storage_dir", title: "Storage directory", kind: .text),
				Field(key: "temp_dir", title: "Temp directory", kind: .text),
				Field(key: "max_storage_gb", title: "Max storage (GB)", kind: .number),
			]
		),
	]

	/// Shown but never editable from here. The GitHub owner/repo/branch rows are
	/// gone with the settings behind them: the app repo is hardcoded and every
	/// scanned repository is configured per source under Channels & Sources, so
	/// those three had been read-only views of three values nothing read.
	private static let _readOnly: [(key: String, title: String)] = [
		("telegram_api_id", "Telegram API ID"),
		("telegram_api_hash", "Telegram API hash"),
		("telegram_phone", "Telegram phone"),
		("github_token", "GitHub token"),
		("ftstore_app_github_token", "Manager proxy token"),
	]

	// MARK: Body

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

			if _settings.isLoading {
				AdminLoadingRow()
			} else if let error = _settings.errorMessage, !_settings.hasLoaded {
				AdminErrorRow(message: error) { Task { await _reload() } }
			} else if _settings.hasLoaded {
				// The descriptor tables above hold `String`, not
				// `LocalizedStringKey`, so every title and footer is looked up
				// here rather than by SwiftUI.
				ForEach(Self._groups) { group in
					Section {
						ForEach(group.fields) { field in
							_row(field)
						}
					} header: {
						Text(String.localized(group.title))
					} footer: {
						if let footer = group.footer {
							Text(String.localized(footer))
						}
					}
				}

				Section {
					ForEach(Self._readOnly, id: \.key) { entry in
						LabeledContent(String.localized(entry.title)) {
							Text(_readOnlyValue(entry.key))
								.foregroundStyle(.secondary)
								.lineLimit(1)
						}
					}
				} header: {
					Text("Credentials")
				} footer: {
					Text("Read-only on purpose. Secrets arrive masked from the server and are edited in the web dashboard.")
				}

				Section {
					NavigationLink {
						AdminBackupView()
					} label: {
						Label("Backup & Restore", systemImage: "arrow.up.arrow.down.square")
					}
				} footer: {
					Text("Export every setting, channel and GitHub source as one JSON file, or restore one.")
				}
			}
		}
		.navigationTitle("Server Settings")
		.navigationBarTitleDisplayMode(.inline)
		.refreshable { await _reload() }
		.task { await _reload() }
		// Single-argument onChange: the two-argument form is iOS 17 and this
		// deploys lower.
		.onChange(of: _focused) { _ in
			_commitEverythingUnfocused()
		}
		// Leaving the screen ends editing without the focus ever moving to
		// another field, so without this the last thing typed would be lost.
		.onDisappear { _commitEverythingUnfocused() }
		.toolbar {
			ToolbarItem(placement: .confirmationAction) {
				if _saving { ProgressView() }
			}
		}
	}

	// MARK: Rows

	@ViewBuilder
	private func _row(_ field: Field) -> some View {
		switch field.kind {
		case .toggle:
			// A switch has no half-flipped state, so it goes the moment it moves.
			Toggle(String.localized(field.title), isOn: _flag(field.key))
		case .number:
			LabeledContent(String.localized(field.title)) {
				// The placeholder is an example value ("ftstore.app", "us"), not
				// prose, so it stays as written.
				TextField(field.placeholder, text: _binding(field.key))
					.keyboardType(.numberPad)
					.multilineTextAlignment(.trailing)
					.focused($_focused, equals: field.key)
					.onSubmit { _commit(field.key) }
			}
		case .text:
			LabeledContent(String.localized(field.title)) {
				TextField(field.placeholder, text: _binding(field.key))
					.textInputAutocapitalization(.never)
					.autocorrectionDisabled()
					.multilineTextAlignment(.trailing)
					.focused($_focused, equals: field.key)
					.onSubmit { _commit(field.key) }
			}
		}
	}

	private func _readOnlyValue(_ key: String) -> String {
		let value = _settings.value?.data.string(key) ?? ""
		return value.isEmpty ? .localized("not set") : value
	}

	// MARK: Bindings

	private func _binding(_ key: String) -> Binding<String> {
		Binding(
			get: { _text[key] ?? "" },
			set: { _text[key] = $0 }
		)
	}

	private func _flag(_ key: String) -> Binding<Bool> {
		Binding(
			get: { _flags[key] ?? false },
			// Moved first so the switch does not sit under a thumb waiting for a
			// round trip; the reload afterwards is what makes it honest again.
			set: { newValue in
				_flags[key] = newValue
				_commit(key)
			}
		)
	}

	// MARK: Loading & saving

	private func _reload() async {
		await _settings.load {
			try await session.get("/api/settings", as: AdminSettingsResponse.self)
		}
		guard let data = _settings.value?.data else { return }

		for group in Self._groups {
			for field in group.fields {
				// The field being typed in is left alone: a reload triggered by
				// saving its neighbour must not overwrite what is under the
				// cursor right now.
				guard field.key != _focused else { continue }

				switch field.kind {
				case .toggle:
					let flag = data.bool(field.key) ?? false
					_flags[field.key] = flag
					_savedFlags[field.key] = flag
				case .number:
					let text = data.int(field.key).map(String.init) ?? ""
					_text[field.key] = text
					_savedText[field.key] = text
				case .text:
					let text = data.string(field.key) ?? ""
					_text[field.key] = text
					_savedText[field.key] = text
				}
			}
		}
	}

	/// Write every text field that has been edited and is no longer focused.
	///
	/// Driven off the focus moving rather than off each keystroke, so a value is
	/// sent once it is finished. Called for *all* unfocused fields rather than
	/// only the one just left, because a keyboard dismissed by tapping the
	/// background moves focus to nil without ever naming what it came from.
	private func _commitEverythingUnfocused() {
		for group in Self._groups {
			for field in group.fields where field.kind != .toggle {
				guard field.key != _focused else { continue }
				_commit(field.key)
			}
		}
	}

	/// Send one setting, if it actually differs from what the server has.
	///
	/// One key per request rather than the whole form. That is what makes saving
	/// on the way past a field safe: an operator editing the scan interval can no
	/// longer write back a stale copy of a domain somebody else changed a minute
	/// ago, which a wholesale PUT did every time it fired.
	private func _commit(_ key: String) {
		guard _settings.hasLoaded else { return }

		guard let field = Self._groups
			.flatMap({ $0.fields })
			.first(where: { $0.key == key })
		else { return }

		let value: AnyCodable
		switch field.kind {
		case .toggle:
			let flag = _flags[key] ?? false
			guard flag != _savedFlags[key] else { return }
			value = AnyCodable(flag)
		case .number:
			// A blanked-out field is left alone rather than written as 0 over a
			// working value.
			guard let number = Int(_text[key] ?? "") else { return }
			guard String(number) != _savedText[key] else { return }
			value = AnyCodable(number)
		case .text:
			let text = _text[key] ?? ""
			guard text != _savedText[key] else { return }
			value = AnyCodable(text)
		}

		// Recorded before the round trip, so a second commit for the same field
		// (focus moving and the view disappearing together) does not send twice.
		switch field.kind {
		case .toggle: _savedFlags[key] = _flags[key] ?? false
		case .number, .text: _savedText[key] = _text[key] ?? ""
		}

		_saving = true
		Task { @MainActor in
			do {
				let ack = try await session.act(
					.put,
					"/api/settings",
					body: [key: value]
				)
				_banner = ack.summary
			} catch {
				_banner = (error as? LocalizedError)?.errorDescription ?? error.localizedDescription
				// Put the snapshot back so the next attempt is not skipped as
				// "unchanged" — a failed write must stay pending, not vanish.
				switch field.kind {
				case .toggle: _savedFlags[key] = nil
				case .number, .text: _savedText[key] = nil
				}
			}
			_saving = false
			await _reload()
		}
	}
}