import Foundation

protocol SummarizationProvider {
	func summarize(transcript: String, date: Date) async throws -> String
}

@Observable
final class SummarizationService {
	var isSummarizing = false

	private let provider: SummarizationProvider

	init(provider: SummarizationProvider = LocalSummarizationProvider()) {
		self.provider = provider
	}

	func generateSummary(for entry: DiaryEntry) async throws -> String {
		guard !entry.combinedTranscript.isEmpty else {
			throw SummarizationError.noTranscript
		}

		isSummarizing = true
		defer { isSummarizing = false }

		return try await provider.summarize(transcript: entry.combinedTranscript, date: entry.date)
	}
}

enum SummarizationError: LocalizedError {
	case noTranscript
	case generationFailed

	var errorDescription: String? {
		switch self {
		case .noTranscript:
			String(localized: "summarization.error.noTranscript")
		case .generationFailed:
			String(localized: "summarization.error.failed")
		}
	}
}

/// Placeholder provider that structures transcripts into a basic diary format.
/// Replace with llama.cpp or other on-device LLM integration.
struct LocalSummarizationProvider: SummarizationProvider {
	func summarize(transcript: String, date: Date) async throws -> String {
		let dateString = date.formatted(.dateTime.day().month(.wide).year().locale(Locale(identifier: "de-DE")))

		// For now, structure the transcript into a basic diary format.
		// This will be replaced with actual LLM inference.
		let lines = transcript.components(separatedBy: .newlines)
			.map { $0.trimmingCharacters(in: .whitespaces) }
			.filter { !$0.isEmpty }

		var result = "# \(dateString)\n\n"
		result += "## Erlebnisse des Tages\n\n"
		result += lines.joined(separator: "\n\n")
		result += "\n"

		return result
	}
}