import Foundation
import SwiftUI
import UniformTypeIdentifiers

@MainActor
final class ImportFlowViewModel: ObservableObject {
	enum FieldMappingState {
		case incomplete
		case partiallyValid
		case valid
	}

	@Published var template = MoodwellStateOfMindTemplate.template
	@Published var entries: [MoodwellEntry] = []
	@Published var sourceKeys: [String] = []
	@Published var mapping = MoodwellStateOfMindTemplate.defaultMapping
	@Published var fieldFormatters: [String: FieldFormatterConfig] = [:]
	@Published var moodValenceScale: [Int: Double] = [1: -0.8, 2: -0.25, 3: 0.3, 4: 0.8]
	@Published var dryRunResult: DryRunResult?
	@Published var isImporting = false
	@Published var statusMessage = ""
	@Published var errorMessage: String?

	let supportedContentTypes: [UTType] = [.json]

	private let healthKitService = HealthKitService()

	init() {
		ensureFormatterDefaults()
		loadBundledSample()
	}

	func loadBundledSample() {
		guard let url = Bundle.main.url(forResource: "MoodwellData", withExtension: "json") else {
			errorMessage = String(localized: "error.sample.missing")
			return
		}
		loadFile(from: url)
	}

	func loadFile(from url: URL) {
		do {
			let data = try Data(contentsOf: url)
			let payload = try JSONDecoder().decode(MoodwellPayload.self, from: data)
			entries = payload.mymoods
			if let firstEntry = payload.mymoods.first {
				sourceKeys = Array(firstEntry.sourceDictionary.keys).sorted()
			} else {
				sourceKeys = []
			}
			ensureFormatterDefaults()
			dryRunResult = nil
			statusMessage = String.localizedStringWithFormat(
				NSLocalizedString("status.loaded", comment: ""),
				entries.count
			)
			errorMessage = nil
		} catch {
			errorMessage = String(localized: "error.load.file") + " \(error.localizedDescription)"
		}
	}

	func runDryRun() {
		let result = MoodwellStateOfMindTemplate.makeDrafts(
			entries: entries,
			mapping: mapping,
			moodValenceScale: moodValenceScale,
			fieldFormatters: fieldFormatters
		)
		dryRunResult = result
		if result.errors.isEmpty {
			statusMessage = String.localizedStringWithFormat(
				NSLocalizedString("status.dryrun.success", comment: ""),
				result.drafts.count
			)
		} else {
			statusMessage = String.localizedStringWithFormat(
				NSLocalizedString("status.dryrun.withErrors", comment: ""),
				result.errors.count
			)
		}
	}

	func commitImport() async {
		guard let dryRunResult else {
			errorMessage = String(localized: "error.dryrun.required")
			return
		}
		guard dryRunResult.errors.isEmpty else {
			errorMessage = String(localized: "error.dryrun.fix")
			return
		}

		isImporting = true
		defer { isImporting = false }

		do {
			try await healthKitService.requestWriteAccessForStateOfMind()
			try await healthKitService.save(dryRunResult.drafts)
			statusMessage = String.localizedStringWithFormat(
				NSLocalizedString("status.import.success", comment: ""),
				dryRunResult.drafts.count
			)
			errorMessage = nil
		} catch {
			errorMessage = String(localized: "error.import.failed") + " \(error.localizedDescription)"
		}
	}

	func sourceExamples(for field: TemplateField, limit: Int = 3) -> [String] {
		let sourceKey = mapping.sourceKey(for: field.id)
		guard !sourceKey.isEmpty else {
			return []
		}

		return entries
			.compactMap { $0.sourceDictionary[sourceKey]?.displayString() }
			.filter { !$0.isEmpty }
			.prefix(limit)
			.map { $0 }
	}

	func formattingPreview(for field: TemplateField) -> FieldFormattingPreview {
		let sourceKey = mapping.sourceKey(for: field.id)
		guard !sourceKey.isEmpty else {
			return FieldFormattingPreview(matched: 0, total: 0, examples: [])
		}

		let formatter = formatter(for: field.id)
		var matched = 0
		var total = 0
		var examples: [String] = []

		for entry in entries {
			guard let raw = entry.sourceDictionary[sourceKey], raw != .null else {
				continue
			}
			guard let rawString = raw.sourceString() else {
				continue
			}
			total += 1
			if
				let transformed = ImportFieldFormatterEngine.apply(sourceText: rawString, config: formatter),
				MoodwellStateOfMindTemplate.validateFormattedTarget(
					fieldID: field.id,
					formatted: transformed,
					moodValenceScale: moodValenceScale
				)
			{
				matched += 1
				if examples.count < 3 {
					examples.append("\(rawString) → \(transformed)")
				}
			}
		}

		return FieldFormattingPreview(matched: matched, total: total, examples: examples)
	}

	func formatter(for fieldID: String) -> FieldFormatterConfig {
		if let formatter = fieldFormatters[fieldID] {
			return formatter
		}
		guard let field = template.fields.first(where: { $0.id == fieldID }) else {
			return .default(for: .string)
		}
		return .default(for: field.type)
	}

	func updateFormatter(for fieldID: String, _ update: (inout FieldFormatterConfig) -> Void) {
		var config = formatter(for: fieldID)
		update(&config)
		fieldFormatters[fieldID] = config
	}

	private func ensureFormatterDefaults() {
		for field in template.fields {
			if fieldFormatters[field.id] == nil {
				fieldFormatters[field.id] = .default(for: field.type)
			}
		}
	}

	func mappedSourceKey(for fieldID: String) -> String {
		mapping.sourceKey(for: fieldID)
	}

	func formatterOptions(for field: TemplateField) -> [FieldFormatterType] {
		switch field.type {
		case .date:
			return [
				.dateISO8601ToISO8601,
				.dateGermanDayMonthYearToISO8601,
				.dateGermanDayMonthYearHourMinuteToISO8601,
				.dateUnixSecondsToISO8601
			]
		default:
			return [.passthrough]
		}
	}

	func formatterDisplayName(_ type: FieldFormatterType) -> String {
		switch type {
		case .passthrough:
			return String(localized: "formatter.option.passthrough")
		case .dateISO8601ToISO8601:
			return String(localized: "formatter.option.date_iso")
		case .dateGermanDayMonthYearToISO8601:
			return String(localized: "formatter.option.date_ddmmyyyy")
		case .dateGermanDayMonthYearHourMinuteToISO8601:
			return String(localized: "formatter.option.date_ddmmyyyy_hhmm")
		case .dateUnixSecondsToISO8601:
			return String(localized: "formatter.option.date_unix_seconds")
		}
	}

	func fieldState(for field: TemplateField) -> FieldMappingState {
		let sourceKey = mappedSourceKey(for: field.id)
		guard !sourceKey.isEmpty else {
			return .incomplete
		}
		let preview = formattingPreview(for: field)
		guard preview.total > 0 else {
			return .incomplete
		}
		return preview.matched == preview.total ? .valid : .partiallyValid
	}

	func fieldStateText(for field: TemplateField) -> String {
		switch fieldState(for: field) {
		case .incomplete:
			return String(localized: "state.incomplete")
		case .partiallyValid:
			return String(localized: "state.partial")
		case .valid:
			return String(localized: "state.valid")
		}
	}

	func previewRows(for field: TemplateField, limit: Int = 5) -> [(input: String, output: String, valid: Bool)] {
		previewRows(for: field, formatterType: formatter(for: field.id).formatterType, limit: limit)
	}

	func previewRows(for field: TemplateField, formatterType: FieldFormatterType, limit: Int = 5) -> [(input: String, output: String, valid: Bool)] {
		let sourceKey = mappedSourceKey(for: field.id)
		guard !sourceKey.isEmpty else {
			return []
		}
		let formatter = FieldFormatterConfig(formatterType: formatterType)

		var rows: [(String, String, Bool)] = []
		for entry in entries {
			guard let raw = entry.sourceDictionary[sourceKey], raw != .null, let input = raw.sourceString() else {
				continue
			}
			let output = ImportFieldFormatterEngine.apply(sourceText: input, config: formatter) ?? ""
			let valid = !output.isEmpty && MoodwellStateOfMindTemplate.validateFormattedTarget(
				fieldID: field.id,
				formatted: output,
				moodValenceScale: moodValenceScale
			)
			rows.append((input, output, valid))
			if rows.count >= limit {
				break
			}
		}
		return rows
	}

	func formatterMatchSummary(for field: TemplateField, formatterType: FieldFormatterType, limit: Int = 5) -> (matched: Int, total: Int) {
		let rows = previewRows(for: field, formatterType: formatterType, limit: limit)
		let matched = rows.filter { $0.valid }.count
		return (matched, rows.count)
	}

	func mappingSummary() -> (validFields: Int, totalFields: Int, validRows: Int, totalRows: Int) {
		var validFields = 0
		var validRows = 0
		var totalRows = 0

		for field in template.fields {
			let preview = formattingPreview(for: field)
			if preview.total > 0 && preview.matched == preview.total {
				validFields += 1
			}
			validRows += preview.matched
			totalRows += preview.total
		}

		return (validFields, template.fields.count, validRows, totalRows)
	}

	func sourceExample(for sourceKey: String) -> String {
		for entry in entries {
			if let value = entry.sourceDictionary[sourceKey]?.sourceString(), !value.isEmpty {
				return value
			}
		}
		return String(localized: "text.no_source_values")
	}
}