import Foundation

public struct PythonRuntime: Equatable {
    public let workingDirectory: URL
    public let python: URL
}

public func parsePythonRuntimeConfig(_ content: String) -> [String: String] {
    var values: [String: String] = [:]
    for rawLine in content.components(separatedBy: .newlines) {
        let line = rawLine.trimmingCharacters(in: .whitespacesAndNewlines)
        guard !line.isEmpty, !line.hasPrefix("#") else { continue }
        let parts = line.split(separator: "=", maxSplits: 1).map(String.init)
        guard parts.count == 2 else { continue }
        let key = parts[0].trimmingCharacters(in: .whitespacesAndNewlines)
        var value = parts[1].trimmingCharacters(in: .whitespacesAndNewlines)
        if value.count >= 2,
           ((value.hasPrefix("\"") && value.hasSuffix("\"")) || (value.hasPrefix("'") && value.hasSuffix("'"))) {
            value.removeFirst()
            value.removeLast()
        }
        guard key == "REYNA_CLI_DIR" || key == "REYNA_CLI_PYTHON" else { continue }
        values[key] = value
    }
    return values
}

public func pythonRuntimeConfig(homeDirectory: URL = FileManager.default.homeDirectoryForCurrentUser) -> [String: String] {
    let paths = [
        homeDirectory.appendingPathComponent(".reyna-cli.env"),
        homeDirectory.appendingPathComponent(".config/reyna-cli/env"),
    ]
    var result: [String: String] = [:]
    for path in paths {
        guard let content = try? String(contentsOf: path, encoding: .utf8) else { continue }
        result.merge(parsePythonRuntimeConfig(content)) { _, newest in newest }
    }
    return result
}

public func resolvePythonRuntime(
    homeDirectory: URL = FileManager.default.homeDirectoryForCurrentUser,
    environment: [String: String] = ProcessInfo.processInfo.environment,
    config: [String: String]? = nil,
    isExecutable: (String) -> Bool = { FileManager.default.isExecutableFile(atPath: $0) }
) -> PythonRuntime {
    let loadedConfig = config ?? pythonRuntimeConfig(homeDirectory: homeDirectory)
    let defaultWorkDirectory = homeDirectory.appendingPathComponent("Projects/reyna-cli").path
    let workDirectoryPath = environment["REYNA_CLI_DIR"] ?? loadedConfig["REYNA_CLI_DIR"] ?? defaultWorkDirectory
    let selectedPython = environment["REYNA_CLI_PYTHON"]
        ?? loadedConfig["REYNA_CLI_PYTHON"]
        ?? URL(fileURLWithPath: workDirectoryPath).appendingPathComponent(".venv/bin/python").path
    let pythonPath = isExecutable(selectedPython) ? selectedPython : "/usr/bin/python3"
    return PythonRuntime(
        workingDirectory: URL(fileURLWithPath: workDirectoryPath),
        python: URL(fileURLWithPath: pythonPath)
    )
}

public func pythonCommand(runtime: PythonRuntime, forwardedArguments: [String]) -> [String] {
    [runtime.python.path, "-m", "reyna_cli.cli"] + forwardedArguments
}

public func pythonLaunchEnvironment(from environment: [String: String] = ProcessInfo.processInfo.environment) -> [String: String] {
    var sanitized = environment
    for key in ["PYTHONHOME", "PYTHONPATH", "VIRTUAL_ENV"] {
        sanitized.removeValue(forKey: key)
    }
    sanitized["PYTHONNOUSERSITE"] = "1"
    return sanitized
}

public func runPythonCLI(forwardedArguments: [String]) -> Int32 {
    let runtime = resolvePythonRuntime()
    let command = pythonCommand(runtime: runtime, forwardedArguments: forwardedArguments)
    let process = Process()
    process.executableURL = runtime.python
    process.arguments = Array(command.dropFirst())
    process.currentDirectoryURL = runtime.workingDirectory
    process.environment = pythonLaunchEnvironment()

    do {
        try process.run()
        process.waitUntilExit()
        return process.terminationStatus
    } catch {
        fputs("error: failed to run Reyna CLI Python: \(error)\n", stderr)
        return 127
    }
}