import Foundation

struct BmlAccountLookupResult: Sendable {
    let accountNumber: String
    let accountName: String
    let bankName: String
    let trnType: String   // "IAT" BML-to-BML, "QTR" Favara, "DOT" other bank
    let bank: String?
}

struct BmlTransferInit: Sendable {
    let code: Int      // 22 = OTP required
}

struct BmlTransferReceipt: Sendable {
    let reference: String
    let timestamp: String
    let message: String
}

// BML 2-step transfer:
//   Step 1 — POST /api/mobile/transfer with transfer details (no otp).
//             Server responds {"success":true,"code":22} when OTP is required.
//   Step 2 — POST same endpoint adding otp field.
//             Server responds {"success":true,"payload":{"reference":...,"timestamp":...}}.
//
// Field names from Kotlin: debitAccount, creditAccount, debitAmount, transfertype, currency, channel, otp, remarks
final class BmlTransferClient {

    private let bmlSession: BmlSession
    private let urlSession: URLSession

    private let base = "https://www.bankofmaldives.com.mv/internetbanking"
    private let ua   = "bml-mobile-banking/348 (Apple; iOS 17.0; iPhone)"
    private let ver  = "2.1.44.348"

    init(bmlSession: BmlSession) {
        self.bmlSession = bmlSession
        let cfg = URLSessionConfiguration.default
        cfg.timeoutIntervalForRequest = 30
        self.urlSession = URLSession(configuration: cfg)
    }

    // MARK: - Account lookup

    func lookupAccount(_ input: String) async throws -> BmlAccountLookupResult {
        let trimmed = input.trimmingCharacters(in: .whitespacesAndNewlines)
        if Self.isMibAccount(trimmed) {
            return try await lookupMibAccount(trimmed)
        }

        // Kotlin uses /api/mobile/validate/account/<input> for BML/Favara validation.
        let data = try await apiGet("/api/mobile/validate/account/\(Self.pathComponent(trimmed))")
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
              root["success"] as? Bool == true,
              let payload = root["payload"] as? [String: Any] else {
            throw BmlError.serverError("Account not found")
        }
        return Self.lookupResult(from: payload, fallbackAccount: trimmed, defaultType: "IAT", defaultBank: nil)
    }

    private func lookupMibAccount(_ account: String) async throws -> BmlAccountLookupResult {
        // Kotlin BmlValidateClient verifies MIB accounts through the Favara account-verification endpoint.
        let data = try await apiGet("/api/mobile/favara/account-verification/\(Self.pathComponent(account))/MIB")
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [String: Any],
              root["success"] as? Bool == true else {
            throw BmlError.serverError("Account not found")
        }
        let payload = root["payload"] as? [String: Any] ?? root
        return Self.lookupResult(from: payload, fallbackAccount: account, defaultType: "DOT", defaultBank: "MIB")
    }

    private static func lookupResult(
        from payload: [String: Any],
        fallbackAccount: String,
        defaultType: String,
        defaultBank: String?
    ) -> BmlAccountLookupResult {
        let trnType = payload["trnType"] as? String
            ?? payload["transferType"] as? String
            ?? defaultType
        let name = payload["name"] as? String
            ?? payload["account_name"] as? String
            ?? payload["accountName"] as? String
            ?? payload["contact_name"] as? String
            ?? payload["BfyNm"] as? String
            ?? ""

        let cdtr = payload["CdtrAcct"] as? [String: Any]
        let account = cdtr?["Acct"] as? String
            ?? payload["account"] as? String
            ?? payload["accountNumber"] as? String
            ?? payload["benefAccount"] as? String
            ?? fallbackAccount
        let bank = payload["bank"] as? String ?? defaultBank
        let bankName = bank == "MIB" ? "Maldives Islamic Bank" : "Bank of Maldives"

        return BmlAccountLookupResult(
            accountNumber: account,
            accountName: name,
            bankName: bankName,
            trnType: trnType,
            bank: bank
        )
    }

    private static func isMibAccount(_ value: String) -> Bool {
        value.count == 17 && value.hasPrefix("9") && value.allSatisfy(\.isNumber)
    }

    private static func pathComponent(_ value: String) -> String {
        value.addingPercentEncoding(withAllowedCharacters: .urlPathAllowed) ?? value
    }

    // MARK: - Step 1: Initiate (no OTP)

    func initiateTransfer(
        fromAccount: BankAccount,
        toAccount: String,
        amount: Double,
        currency: String,
        trnType: String,
        bank: String?
    ) async throws -> BmlTransferInit {
        let debitAccount = try debitAccountCode(fromAccount)
        var body: [String: Any] = [
            "debitAccount":  debitAccount,
            "creditAccount": toAccount,
            "debitAmount":   amount,
            "transfertype":  trnType,
            "currency":      currency,
            "channel":       "token"
        ]
        if let bank, !bank.isEmpty {
            body["bank"] = bank
        }

        let data = try await apiPost("/api/mobile/transfer", body: body)
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            throw BmlError.invalidResponse
        }
        guard root["success"] as? Bool == true else {
            let msg    = root["message"] as? String ?? ""
            let code   = root["code"] as? Int
            let extra  = (root["payload"] as? [String: Any])?["message"] as? String ?? ""
            let full   = [msg, extra].filter { !$0.isEmpty }.joined(separator: " — ")
            let suffix = code.map { " (code \($0))" } ?? ""
            throw BmlError.serverError(full.isEmpty ? "Transfer failed\(suffix)" : "\(full)\(suffix)")
        }
        return BmlTransferInit(code: root["code"] as? Int ?? 0)
    }

    // MARK: - Step 2: Confirm with OTP

    func confirmTransfer(
        fromAccount: BankAccount,
        toAccount: String,
        amount: Double,
        currency: String,
        trnType: String,
        remarks: String,
        otp: String,
        bank: String?
    ) async throws -> BmlTransferReceipt {
        let debitAccount = try debitAccountCode(fromAccount)
        var body: [String: Any] = [
            "debitAccount":  debitAccount,
            "creditAccount": toAccount,
            "debitAmount":   amount,
            "transfertype":  trnType,
            "currency":      currency,
            "channel":       "token",
            "otp":           otp
        ]
        if !remarks.isEmpty {
            body["remarks"] = remarks
        }
        if let bank, !bank.isEmpty {
            body["bank"] = bank
        }

        let data = try await apiPost("/api/mobile/transfer", body: body)
        guard let root = try? JSONSerialization.jsonObject(with: data) as? [String: Any] else {
            throw BmlError.invalidResponse
        }
        guard root["success"] as? Bool == true else {
            let msg    = root["message"] as? String ?? ""
            let code   = root["code"] as? Int
            let extra  = (root["payload"] as? [String: Any])?["message"] as? String ?? ""
            let full   = [msg, extra].filter { !$0.isEmpty }.joined(separator: " — ")
            let suffix = code.map { " (code \($0))" } ?? ""
            throw BmlError.serverError(full.isEmpty ? "Transfer confirmation failed\(suffix)" : "\(full)\(suffix)")
        }
        let payload = root["payload"] as? [String: Any] ?? [:]
        return BmlTransferReceipt(
            reference: payload["reference"] as? String ?? "",
            timestamp: payload["timestamp"] as? String ?? "",
            message:   root["message"] as? String ?? "Transfer successful"
        )
    }

    private func debitAccountCode(_ account: BankAccount) throws -> String {
        let code = (account.internalId ?? "").trimmingCharacters(in: .whitespacesAndNewlines)
        guard !code.isEmpty else {
            throw BmlError.serverError("BML debit account id missing. Refresh dashboard and select the account again.")
        }
        return code
    }

    // MARK: - HTTP

    private func apiGet(_ path: String) async throws -> Data {
        var req = URLRequest(url: URL(string: "\(base)\(path)")!)
        req.setValue("Bearer \(bmlSession.accessToken)", forHTTPHeaderField: "Authorization")
        req.setValue(ua,  forHTTPHeaderField: "User-Agent")
        req.setValue(ver, forHTTPHeaderField: "x-app-version")
        let (data, resp) = try await urlSession.data(for: req)
        let code = (resp as? HTTPURLResponse)?.statusCode ?? 0
        if code == 401 || code == 419 { throw BmlError.sessionExpired }
        if code >= 500 { throw BmlError.networkError("HTTP \(code)") }
        return data
    }

    private func apiPost(_ path: String, body: [String: Any]) async throws -> Data {
        var req = URLRequest(url: URL(string: "\(base)\(path)")!)
        req.httpMethod = "POST"
        req.setValue("Bearer \(bmlSession.accessToken)", forHTTPHeaderField: "Authorization")
        req.setValue(ua,                  forHTTPHeaderField: "User-Agent")
        req.setValue(ver,                 forHTTPHeaderField: "x-app-version")
        req.setValue("application/json",  forHTTPHeaderField: "Content-Type")
        req.httpBody = try? JSONSerialization.data(withJSONObject: body)
        let (data, resp) = try await urlSession.data(for: req)
        let code = (resp as? HTTPURLResponse)?.statusCode ?? 0
        if code == 401 || code == 419 { throw BmlError.sessionExpired }
        if code >= 500 { throw BmlError.networkError("HTTP \(code)") }
        return data
    }
}