import Foundation

/// Mirrors internal/protocols/hysteria2 config_write.go + endpoint.go (SOCKS 1080 / HTTP 1081).
enum Hy2ConfigBuilder {
    struct Endpoint {
        var server: String
        var auth: String = ""
        var sni: String = ""
        var insecure: Bool = false
        var pinSHA256: String = ""
        var obfs: String = ""
        var obfsPassword: String = ""
    }

    static func buildYAML(uri: String, socks: String = "127.0.0.1:1080", http: String = "127.0.0.1:1081") throws -> String {
        let ep = try parseEndpoint(uri)
        var b = "# generated by Navis — do not edit\n"
        b += "server: \(yamlQuote(ep.server))\n"
        if !ep.auth.isEmpty {
            b += "auth: \(yamlQuote(ep.auth))\n"
        }
        if !ep.sni.isEmpty || ep.insecure || !ep.pinSHA256.isEmpty {
            b += "tls:\n"
            if !ep.sni.isEmpty {
                b += "  sni: \(yamlQuote(ep.sni))\n"
            }
            if ep.insecure {
                b += "  insecure: true\n"
            }
            if !ep.pinSHA256.isEmpty {
                b += "  pinSHA256: \(yamlQuote(ep.pinSHA256))\n"
            }
        }
        let obfs = ep.obfs.lowercased()
        switch obfs {
        case "salamander":
            if ep.obfsPassword.isEmpty {
                throw BuilderError.message("hysteria2: salamander требует пароль (obfs-password)")
            }
            b += "obfs:\n  type: salamander\n  salamander:\n    password: \(yamlQuote(ep.obfsPassword))\n"
        case "gecko":
            if ep.obfsPassword.isEmpty {
                throw BuilderError.message("hysteria2: gecko требует пароль (obfs-password)")
            }
            b += "obfs:\n  type: gecko\n  gecko:\n    password: \(yamlQuote(ep.obfsPassword))\n"
        default:
            break
        }
        // Default BBR like desktop when no bandwidth overrides.
        b += "congestion:\n  type: bbr\n  bbrProfile: standard\n"
        b += "socks5:\n  listen: \(yamlQuote(socks))\n"
        b += "http:\n  listen: \(yamlQuote(http))\n"
        return b
    }

    static func parseEndpoint(_ raw: String) throws -> Endpoint {
        var s = raw.trimmingCharacters(in: .whitespacesAndNewlines)
        if let hash = s.firstIndex(of: "#") {
            s = String(s[..<hash])
        }
        let lower = s.lowercased()
        if lower.hasPrefix("hy2://") {
            s = "hysteria2://" + String(s.dropFirst("hy2://".count))
        }
        guard lower.hasPrefix("hysteria2://") || s.lowercased().hasPrefix("hysteria2://") else {
            throw BuilderError.message("ожидалась ссылка hysteria2:// или hy2://")
        }
        guard let u = URLComponents(string: s) else {
            throw BuilderError.message("parse hysteria2 URI")
        }
        guard let host = u.host, !host.isEmpty else {
            throw BuilderError.message("hysteria2 URI missing host")
        }
        var server = host
        if let port = u.port {
            server = "\(host):\(port)"
        } else if let h = u.percentEncodedHost ?? u.host {
            // URLComponents may put multi-port in host; prefer raw host field from string.
            if let at = s.range(of: "://") {
                var rest = String(s[at.upperBound...])
                if let slash = rest.firstIndex(of: "/") { rest = String(rest[..<slash]) }
                if let q = rest.firstIndex(of: "?") { rest = String(rest[..<q]) }
                if let atSign = rest.firstIndex(of: "@") {
                    rest = String(rest[rest.index(after: atSign)...])
                }
                if !rest.isEmpty { server = rest }
            }
        }

        var auth = ""
        if let user = u.user {
            if let pass = u.password {
                auth = "\(user):\(pass)"
            } else {
                auth = user.removingPercentEncoding ?? user
            }
        }
        let q = Dictionary(uniqueKeysWithValues: (u.queryItems ?? []).map { ($0.name, $0.value ?? "") })
        var ep = Endpoint(server: server, auth: auth)
        ep.sni = first(q, "sni", "peer")
        ep.pinSHA256 = first(q, "pinSHA256", "pinsha256")
        ep.obfs = first(q, "obfs")
        ep.obfsPassword = first(q, "obfs-password", "obfs_password")
        let insc = first(q, "insecure")
        ep.insecure = insc == "1" || insc.lowercased() == "true"
        return ep
    }

    private static func first(_ q: [String: String], _ keys: String...) -> String {
        for k in keys {
            if let v = q[k], !v.trimmingCharacters(in: .whitespaces).isEmpty {
                return v.trimmingCharacters(in: .whitespaces)
            }
        }
        return ""
    }

    private static func yamlQuote(_ s: String) -> String {
        if s.isEmpty { return "\"\"" }
        if s.contains(where: { ":#{}[],&*?|-<>=!%@`'\"".contains($0) || $0.isWhitespace }) {
            let escaped = s.replacingOccurrences(of: "\\", with: "\\\\").replacingOccurrences(of: "\"", with: "\\\"")
            return "\"\(escaped)\""
        }
        return s
    }
}