import Foundation

enum FanControlError: LocalizedError {
    case backendUnavailable
    case commandFailed(String)

    var errorDescription: String? {
        switch self {
        case .backendUnavailable:
            "The SMC control backend is unavailable on this Mac."
        case .commandFailed(let message):
            message.isEmpty ? "The fan command did not complete." : message
        }
    }
}

enum FanControlService {
    static var toolPath: String {
        if let bundled = Bundle.main.url(forResource: "smc", withExtension: nil)?.path,
           FileManager.default.isExecutableFile(atPath: bundled) {
            return bundled
        }
        return "/Applications/Stats.app/Contents/Resources/smc"
    }

    static var isAvailable: Bool {
        FileManager.default.isExecutableFile(atPath: toolPath)
    }

    static func setManualTargets(_ targets: [Int: Double]) throws {
        guard isAvailable else { throw FanControlError.backendUnavailable }
        let commands = targets.sorted { $0.key < $1.key }.flatMap { id, speed in
            let safeID = max(0, id)
            let safeSpeed = max(0, Int(speed.rounded()))
            return ["\(quotedTool) fan \(safeID) -m 1", "\(quotedTool) fan \(safeID) -v \(safeSpeed)"]
        }
        try runPrivileged(commands.joined(separator: " && "))
    }

    static func restoreAutomatic() throws {
        guard isAvailable else { throw FanControlError.backendUnavailable }
        try runPrivileged("\(quotedTool) reset")
    }

    private static var quotedTool: String {
        "'" + toolPath.replacingOccurrences(of: "'", with: "'\\''") + "'"
    }

    private static func runPrivileged(_ shellCommand: String) throws {
        let escaped = shellCommand
            .replacingOccurrences(of: "\\", with: "\\\\")
            .replacingOccurrences(of: "\"", with: "\\\"")
        let script = "do shell script \"\(escaped)\" with administrator privileges"
        let process = Process()
        let errorPipe = Pipe()
        process.executableURL = URL(fileURLWithPath: "/usr/bin/osascript")
        process.arguments = ["-e", script]
        process.standardOutput = FileHandle.nullDevice
        process.standardError = errorPipe
        try process.run()
        let errorData = errorPipe.fileHandleForReading.readDataToEndOfFile()
        process.waitUntilExit()
        guard process.terminationStatus == 0 else {
            throw FanControlError.commandFailed(String(decoding: errorData, as: UTF8.self).trimmingCharacters(in: .whitespacesAndNewlines))
        }
    }
}