import Foundation
#if canImport(FoundationModels)
import FoundationModels
#endif

/// Splits a single free-form phrase (typically dictated, e.g. "two onions, half
/// a litre of milk and some olive oil") into individual, normalized ingredient
/// lines. Uses Apple's on-device Foundation Models when available for smart
/// parsing of quantities and natural-language separators; otherwise falls back
/// to a lightweight heuristic splitter. Fully local and never throws.
enum IngredientParser {

    /// Parses `text` into clean ingredient lines, kept in `language`.
    static func parse(_ text: String, language: AppLanguage) async -> [String] {
        let trimmed = text.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !trimmed.isEmpty else { return [] }

        #if canImport(FoundationModels)
        if #available(iOS 26.0, *), case .available = SystemLanguageModel.default.availability {
            let langName = language.resolved().displayName
            let instructions = """
            You split a spoken grocery list into individual ingredients. The user \
            dictates several ingredients in one sentence, separated by commas, the \
            word "and", or natural pauses. Output ONE ingredient per line, keeping \
            any quantity the user actually said (e.g. "2 onions", "500 g flour"). \
            Do not invent ingredients, do not add quantities that were not said, \
            do not number or bullet the lines, and add no commentary. Keep the \
            ingredients written in \(langName).
            """
            do {
                let session = LanguageModelSession(instructions: instructions)
                let response = try await session.respond(to: trimmed)
                let lines = IngredientGenerator.parseLines(response.content)
                if !lines.isEmpty { return lines }
            } catch {
                CrashlyticsService.record(error, context: "ingredient_parsing")
            }
        }
        #endif

        return heuristicSplit(trimmed)
    }

    /// Splits on newlines, commas, semicolons and standalone conjunctions
    /// ("and"/"y"/"e"/"et"/"und") when the on-device model is unavailable.
    static func heuristicSplit(_ text: String) -> [String] {
        let separators = CharacterSet(charactersIn: ",;\n•")
        let conjunctions = [" y ", " e ", " and ", " et ", " und "]
        return text
            .components(separatedBy: separators)
            .flatMap { piece -> [String] in
                var parts = [piece]
                for conjunction in conjunctions {
                    parts = parts.flatMap { $0.components(separatedBy: conjunction) }
                }
                return parts
            }
            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
            .filter { !$0.isEmpty }
    }
}