#!/usr/bin/env python3
"""
security_linter.py — Scan code for security vulnerabilities.

Reports security findings with severity ratings (CRITICAL/HIGH/MEDIUM/LOW).
Outputs a JSON security lint report.

Usage:
    python3 security_linter.py --path .
    python3 security_linter.py --path . --output security_report.json
    python3 security_linter.py --path . --format json  # default
    python3 security_linter.py --path . --format markdown
"""

import argparse
import json
import re
import sys
from pathlib import Path
from typing import List, Dict, Any, Optional


SEVERITY_CRITICAL = "CRITICAL"
SEVERITY_HIGH = "HIGH"
SEVERITY_MEDIUM = "MEDIUM"
SEVERITY_LOW = "LOW"


class SecurityFinding:
    """Represents a security finding."""

    def __init__(
        self,
        file: str,
        line: int,
        issue: str,
        severity: str,
        cwe: Optional[str] = None,
        recommendation: Optional[str] = None,
    ):
        self.file = file
        self.line = line
        self.issue = issue
        self.severity = severity
        self.cwe = cwe
        self.recommendation = recommendation

    def to_dict(self) -> Dict[str, Any]:
        return {
            "file": self.file,
            "line": self.line,
            "issue": self.issue,
            "severity": self.severity,
            "cwe": self.cwe,
            "recommendation": self.recommendation,
        }


# Pattern entries: (pattern_regex, description, severity, cwe, recommendation)
# Pattern strings use normal strings (not raw) to allow ['"] character classes without
# backslash-injection issues. \s and \b are escaped to give \s and \b in the actual regex.
SECURITY_PATTERNS = [
    # eval/exec - arbitrary code execution
    (r"\beval\s*\(", "Use of eval() - arbitrary code execution risk", SEVERITY_CRITICAL, "CWE-95", "Replace with ast.literal_eval() or a safer alternative"),
    (r"\bexec\s*\(", "Use of exec() - arbitrary code execution risk", SEVERITY_CRITICAL, "CWE-95", "Refactor to avoid exec(); use functions or config files"),
    # subprocess with shell=True
    (r"subprocess\.(?:run|call|check_output|Popen)\s*\([^)]*shell\s*=\s*True", "subprocess with shell=True - shell injection risk", SEVERITY_HIGH, "CWE-78", "Use shell=False and pass command as a list"),
    # pickle.loads - arbitrary code execution
    (r"pickle\.loads?\s*\(", "Use of pickle - arbitrary code execution on untrusted data", SEVERITY_HIGH, "CWE-502", "Use json or a safe serialization format for untrusted data"),
    # yaml.load without Loader
    (r"yaml\.load\s*\(", "yaml.load() - unsafe deserialization", SEVERITY_HIGH, "CWE-502", "Use yaml.safe_load()"),
    # tempfile.mktemp - insecure temp file creation
    (r"tempfile\.mktemp\s*\(", "tempfile.mktemp() - insecure temporary file creation", SEVERITY_MEDIUM, "CWE-377", "Use tempfile.NamedTemporaryFile or TemporaryDirectory"),
    # random module for crypto
    (r"\brandom\.(?:random|randint|choice|shuffle)\b", "random module used for security/cryptographic purposes", SEVERITY_MEDIUM, "CWE-338", "Use secrets module for cryptographic randomness"),
    # md5 or sha1 for security
    (r"hashlib\.(?:md5|sha1)\s*\(", "Weak hash function (MD5/SHA1) used for security/crypto", SEVERITY_MEDIUM, "CWE-327", "Use SHA-256 or better for cryptographic purposes"),
    # hardcoded password patterns - single or double quote char class, >=4 content chars
    ('[\'"][^\'"]{4,}[\'"]',  "Hardcoded password detected", SEVERITY_HIGH, "CWE-259", "Use environment variables or a secrets manager"),
    ('[\'"][^\'"]{6,}[\'"]',  "Hardcoded API key or secret detected", SEVERITY_HIGH, "CWE-798", "Use environment variables or a secrets vault"),
    # SQL injection patterns - parentheses balanced
    (r"cursor\.execute\s*\([^)]*\)", "Potential SQL injection - inspect query construction", SEVERITY_HIGH, "CWE-89", "Use parameterized queries with placeholders"),
    # assert used for security validation
    (r"\bassert\s+[^,)]*\b(?:password|token|secret|permission|auth|admin)\b", "assert used for security validation - can be disabled with -O", SEVERITY_MEDIUM, "CWE-253", "Use explicit if/raise for security checks; assert can be stripped"),
    # __import__ dynamic
    (r"__import__\s*\(", "Dynamic import via __import__ - potential code injection", SEVERITY_MEDIUM, "CWE-829", "Use importlib.import_module with validated module names"),
]


def scan_file(path: Path) -> List[SecurityFinding]:
    findings = []
    try:
        with open(path, "r", encoding="utf-8", errors="ignore") as f:
            lines = f.readlines()
    except (OSError, UnicodeDecodeError):
        return findings

    for line_num, line in enumerate(lines, start=1):
        for pattern, issue, severity, cwe, recommendation in SECURITY_PATTERNS:
            if re.search(pattern, line):
                findings.append(
                    SecurityFinding(
                        file=str(path),
                        line=line_num,
                        issue=issue,
                        severity=severity,
                        cwe=cwe,
                        recommendation=recommendation,
                    )
                )
    return findings


def scan_directory(path: Path, extensions=None) -> List[SecurityFinding]:
    if extensions is None:
        extensions = {".py"}
    findings = []
    if not path.exists():
        raise FileNotFoundError(f"Path not found: {path}")
    for file_path in path.rglob("*"):
        if file_path.is_file() and file_path.suffix in extensions:
            findings.extend(scan_file(file_path))
    return findings


def generate_json_report(findings: List[SecurityFinding]) -> Dict[str, Any]:
    by_severity = {SEVERITY_CRITICAL: [], SEVERITY_HIGH: [], SEVERITY_MEDIUM: [], SEVERITY_LOW: []}
    for f in findings:
        by_severity[f.severity].append(f.to_dict())
    severity_counts = {s: len(v) for s, v in by_severity.items()}
    total = sum(severity_counts.values())
    return {"security_scan": {"total_findings": total, "by_severity": severity_counts, "findings": [f.to_dict() for f in findings]}}


def generate_markdown_report(findings: List[SecurityFinding]) -> str:
    by_severity = {SEVERITY_CRITICAL: [], SEVERITY_HIGH: [], SEVERITY_MEDIUM: [], SEVERITY_LOW: []}
    for f in findings:
        by_severity[f.severity].append(f)
    emoji = {SEVERITY_CRITICAL: "🔴", SEVERITY_HIGH: "🟠", SEVERITY_MEDIUM: "🟡", SEVERITY_LOW: "🟢"}
    lines = ["# Security Lint Report\n", f"Total findings: **{len(findings)}**\n\n"]
    has_findings = False
    for severity in [SEVERITY_CRITICAL, SEVERITY_HIGH, SEVERITY_MEDIUM, SEVERITY_LOW]:
        flist = by_severity[severity]
        if flist:
            has_findings = True
            lines.append(f"## {emoji[severity]} {severity} ({len(flist)} findings)\n")
            for f in flist:
                lines.append(f"- **{f.file}:{f.line}** — {f.issue}")
            lines.append("")
    if not has_findings:
        lines.append("✅ No security issues found.\n")
    return "\n".join(lines)


def main():
    parser = argparse.ArgumentParser(description="Scan code for security vulnerabilities")
    parser.add_argument("--path", type=Path, default=Path("."), help="Path to scan (file or directory)")
    parser.add_argument("--output", "-o", type=Path, default=None, help="Output file")
    parser.add_argument("--format", choices=["json", "markdown"], default="json", help="Output format (default: json)")
    parser.add_argument("--extensions", type=str, default=".py", help="Comma-separated file extensions (default: .py)")
    args = parser.parse_args()
    exts = {e.strip() for e in args.extensions.split(",")}
    findings = scan_directory(args.path, extensions=exts)
    output = json.dumps(generate_json_report(findings), indent=2) if args.format == "json" else generate_markdown_report(findings)
    if args.output:
        args.output.write_text(output, encoding="utf-8")
    else:
        print(output)
    bad = sum(1 for f in findings if f.severity in (SEVERITY_CRITICAL, SEVERITY_HIGH))
    sys.exit(1 if bad > 0 else 0)


if __name__ == "__main__":
    main()