import Foundation
import UIKit

/// VL 解析结果(已结构化,可直接喂 SwiftData 模型构造)。
/// 与 Indicator/Report 字段近似但解耦 —— 这样 prompt schema 调整不污染数据层。
struct ParsedReport: Sendable {
    var title: String
    var typeRaw: String
    var reportDate: Date
    var institution: String
    var summary: String
    var pageCount: Int
    var indicators: [ParsedIndicator]

    struct ParsedIndicator: Sendable {
        var name: String
        var value: String
        var unit: String
        var range: String
        var status: IndicatorStatus
    }

    /// 一项都没识别出来 = 视作失败,UI 走手动录入回退。
    var isEmpty: Bool { indicators.isEmpty }

    /// 占位空结果,失败回退时给 UI。
    static func empty(date: Date = .now) -> ParsedReport {
        ParsedReport(
            title: "",
            typeRaw: ReportType.other.rawValue,
            reportDate: date,
            institution: "",
            summary: "",
            pageCount: 1,
            indicators: []
        )
    }
}

/// CaptureService 错误 — UI 决定怎么呈现(回退表单 vs 重试)。
enum CaptureError: Error, LocalizedError {
    case modelNotReady
    case writeAssetFailed
    case inferenceFailed(String)
    case parseFailed(String)

    var errorDescription: String? {
        switch self {
        case .modelNotReady:           return "VL 模型尚未就绪"
        case .writeAssetFailed:        return "图片保存失败"
        case .inferenceFailed(let m):  return "识别失败:\(m)"
        case .parseFailed(let m):      return "结构化失败:\(m)"
        }
    }
}

/// `CaptureService` 是 actor 是因为它的方法会等 AIRuntime(也是 actor),
/// 但本身不持任何可变状态 —— 单例 stateless,纯粹是 §3.1 模块边界的"门面"。
actor CaptureService {
    static let shared = CaptureService()
    private init() {}

    /// 写图 + VL 推理 + 解析 → ParsedReport。
    /// 任何阶段失败,都抛 CaptureError;UI 接住后切到「手动录入」表单。
    /// - Returns: (ParsedReport, [FileVault.SavedAsset]) 元组,
    ///   SavedAsset 列表用于后续构造 Asset @Model。
    func analyze(images: [UIImage]) async throws
        -> (parsed: ParsedReport, assets: [FileVault.SavedAsset]) {

        // 1. 写图到 Vault(全程加密目录)
        let assets: [FileVault.SavedAsset]
        do {
            assets = try images.map { try FileVault.shared.writeJPEG($0) }
        } catch {
            throw CaptureError.writeAssetFailed
        }

        // 2. VL 推理
        try await AIRuntime.shared.prepareVL()
        let urls = assets.map { FileVault.shared.rootURL.appendingPathComponent($0.relativePath) }
        let raw: String
        do {
            raw = try await AIRuntime.shared.analyzeReport(
                imageURLs: urls,
                prompt: VLPrompts.reportExtraction
            )
        } catch {
            throw CaptureError.inferenceFailed("\(error)")
        }

        // 3. JSON 解析(带容错:可能包含围栏 / 前后文字)
        do {
            let parsed = try CaptureService.parseReportJSON(raw, pageCount: assets.count)
            return (parsed, assets)
        } catch let CaptureError.parseFailed(msg) {
            throw CaptureError.parseFailed(msg)
        } catch {
            throw CaptureError.parseFailed("\(error)")
        }
    }

    // MARK: - JSON parse(static + 纯函数 → 方便单测)

    /// 从 VL 输出里抠出第一段合法 JSON 对象并解析。
    /// 容错:
    /// - 去掉 ```json``` markdown 围栏
    /// - 去掉首尾非 JSON 文字
    /// - 缺字段填默认值
    /// 解析不到任何 indicator 也算成功,但 ParsedReport.isEmpty = true,
    /// UI 走「手动录入」分支。
    static func parseReportJSON(_ raw: String, pageCount: Int = 1) throws -> ParsedReport {
        let jsonString = extractJSONObject(from: raw)
        guard let data = jsonString.data(using: .utf8) else {
            throw CaptureError.parseFailed("非 UTF-8 输出")
        }
        let obj: Any
        do {
            obj = try JSONSerialization.jsonObject(with: data, options: [.fragmentsAllowed])
        } catch {
            throw CaptureError.parseFailed("JSON 不合法:\(error.localizedDescription)")
        }
        guard let dict = obj as? [String: Any] else {
            throw CaptureError.parseFailed("根节点不是对象")
        }

        let title = (dict["title"] as? String)?.trimmingCharacters(in: .whitespaces) ?? ""
        let typeRaw = parseReportType(dict["type"] as? String)
        let reportDate = parseDate(dict["report_date"] as? String) ?? .now
        let institution = (dict["institution"] as? String) ?? ""
        let summary = (dict["summary"] as? String) ?? ""
        let pages = (dict["page_count"] as? Int) ?? pageCount

        let indicatorsRaw = (dict["indicators"] as? [[String: Any]]) ?? []
        let indicators: [ParsedReport.ParsedIndicator] = indicatorsRaw.compactMap {
            parseIndicator($0)
        }

        return ParsedReport(
            title: title.isEmpty ? "拍摄识别" : title,
            typeRaw: typeRaw,
            reportDate: reportDate,
            institution: institution,
            summary: summary,
            pageCount: max(pages, pageCount),
            indicators: indicators
        )
    }

    /// 从字符串里抠出第一段平衡的 {...}。处理 markdown 围栏、前后乱码。
    /// 失败返回原字符串(后续 JSONSerialization 报错)。
    static func extractJSONObject(from raw: String) -> String {
        var s = raw.trimmingCharacters(in: .whitespacesAndNewlines)

        // 去 markdown 围栏
        if s.hasPrefix("```") {
            // 砍掉首行 ```json 或 ```
            if let firstNewline = s.firstIndex(of: "\n") {
                s = String(s[s.index(after: firstNewline)...])
            }
            // 砍掉末尾 ```
            if let endRange = s.range(of: "```", options: .backwards) {
                s = String(s[..<endRange.lowerBound])
            }
            s = s.trimmingCharacters(in: .whitespacesAndNewlines)
        }

        // 找第一个 {,然后括号配对到匹配的 }
        guard let start = s.firstIndex(of: "{") else { return s }
        var depth = 0
        var inString = false
        var escape = false
        var idx = start
        while idx < s.endIndex {
            let ch = s[idx]
            if escape { escape = false }
            else if ch == "\\" { escape = true }
            else if ch == "\"" { inString.toggle() }
            else if !inString {
                if ch == "{" { depth += 1 }
                else if ch == "}" {
                    depth -= 1
                    if depth == 0 {
                        return String(s[start...idx])
                    }
                }
            }
            idx = s.index(after: idx)
        }
        return String(s[start...])
    }

    private static func parseReportType(_ raw: String?) -> String {
        guard let raw = raw?.lowercased() else { return ReportType.other.rawValue }
        return ReportType(rawValue: raw)?.rawValue ?? ReportType.other.rawValue
    }

    private static func parseDate(_ raw: String?) -> Date? {
        guard let s = raw?.trimmingCharacters(in: .whitespaces), !s.isEmpty else { return nil }
        let f = DateFormatter()
        f.locale = Locale(identifier: "en_US_POSIX")
        f.dateFormat = "yyyy-MM-dd"
        return f.date(from: s)
    }

    private static func parseIndicator(_ d: [String: Any]) -> ParsedReport.ParsedIndicator? {
        guard let name = (d["name"] as? String)?.trimmingCharacters(in: .whitespaces),
              !name.isEmpty else { return nil }
        let value: String
        if let v = d["value"] as? String { value = v }
        else if let v = d["value"] as? NSNumber { value = v.stringValue }
        else { value = "" }
        let unit = (d["unit"] as? String) ?? ""
        let range = (d["range"] as? String) ?? ""
        let statusRaw = (d["status"] as? String)?.lowercased() ?? "normal"
        let status = IndicatorStatus(rawValue: statusRaw) ?? .normal
        return .init(name: name, value: value, unit: unit, range: range, status: status)
    }
}