import Foundation

struct ParsedDiagnostic {
    let filePath: String
    let line:     Int
    let column:   Int
    let severity: DiagnosticRange.Severity
    let message:  String

    func toDiagnosticRange() -> DiagnosticRange {
        DiagnosticRange(line: line, column: column, length: 40,
                        severity: severity, message: message)
    }
}

struct BuildDiagnosticParser {
    private static let pattern = try! NSRegularExpression(
        pattern: #"^(.+\.swift):(\d+):(\d+):\s+(error|warning|note):\s+(.+)$"#
    )

    static func parse(_ lines: [String]) -> [ParsedDiagnostic] {
        lines.compactMap { parseLine($0) }
    }

    private static func parseLine(_ line: String) -> ParsedDiagnostic? {
        let range = NSRange(line.startIndex..., in: line)
        guard let match = pattern.firstMatch(in: line, range: range) else { return nil }
        func g(_ i: Int) -> String? {
            guard let r = Range(match.range(at: i), in: line) else { return nil }
            return String(line[r])
        }
        guard let path = g(1), let lineStr = g(2), let lineNum = Int(lineStr),
              let colStr = g(3),  let colNum  = Int(colStr),
              let sev    = g(4),  let msg     = g(5) else { return nil }
        return ParsedDiagnostic(filePath: path, line: lineNum, column: colNum,
                                severity: sev == "error" ? .error : .warning, message: msg)
    }
}