#!/usr/bin/env python3
"""Passcheck — password strength auditor."""
import argparse, math, re, sys, string


def color(text, code):
    return f"\033[{code}m{text}\033[0m" if sys.stdout.isatty() else text


COMMON_PATTERNS = [
    r"password", r"1234", r"qwerty", r"abc123", r"letmein",
    r"admin", r"welcome", r"monkey", r"dragon", r"master",
    r"123456", r"passw0rd", r"iloveyou", r"sunshine",
    r"princess", r"football", r"baseball", r"trustno1",
]


def entropy(password):
    char_sets = 0
    if re.search(r"[a-z]", password): char_sets += 26
    if re.search(r"[A-Z]", password): char_sets += 26
    if re.search(r"[0-9]", password): char_sets += 10
    if re.search(r"[!@#$%^&*()_+\-=\[\]{}|;:,.<>?/~`]", password): char_sets += 32
    
    if char_sets == 0:
        return 0
    
    ent = len(password) * math.log2(char_sets)
    return ent


def analyze(password):
    issues = []
    score = 100
    
    # Length checks
    if len(password) < 8:
        score -= 25
        issues.append("Too short ( < 8 chars )")
    elif len(password) < 12:
        score -= 10
        issues.append("Could be longer ( < 12 chars )")
    
    # Character diversity
    if not re.search(r"[a-z]", password):
        score -= 10
        issues.append("Missing lowercase letters")
    if not re.search(r"[A-Z]", password):
        score -= 10
        issues.append("Missing uppercase letters")
    if not re.search(r"[0-9]", password):
        score -= 10
        issues.append("Missing digits")
    if not re.search(r"[!@#$%^&*()_+\-=\[\]{}|;:,.<>?/~`]", password):
        score -= 10
        issues.append("Missing special characters")
    
    # Repeated chars
    if re.search(r"(.)\1{3,}", password):
        score -= 10
        issues.append("Contains repeated characters (aaa)")
    
    # Sequential
    seqs = ["abcdefghijklmnopqrstuvwxyz", "0123456789",
            "qwertyuiop", "asdfghjkl", "zxcvbnm"]
    lower = password.lower()
    for seq in seqs:
        for i in range(len(seq) - 2):
            if seq[i:i+3] in lower:
                score -= 10
                issues.append(f"Contains sequential pattern '{seq[i:i+3]}'")
                break
    
    # Common patterns
    for pattern in COMMON_PATTERNS:
        if pattern in password.lower():
            score -= 20
            issues.append(f"Contains common pattern '{pattern}'")
            break
    
    # Entropy
    ent = entropy(password)
    if ent < 30:
        score -= 15
        issues.append(f"Low entropy ({ent:.1f} bits)")
    
    score = max(0, min(100, score))
    
    # Grade
    if score >= 80:
        grade = color("Strong", "32")
    elif score >= 60:
        grade = color("Moderate", "33")
    elif score >= 40:
        grade = color("Weak", "31")
    else:
        grade = color("Very Weak", "31;1")
    
    return score, grade, ent, issues


def main():
    parser = argparse.ArgumentParser(
        description="Passcheck — password strength auditor",
        formatter_class=argparse.RawDescriptionHelpFormatter,
        epilog=(
            "Examples:\n"
            "  passcheck                         # Interactive mode\n"
            "  echo 'mypassword' | passcheck     # Read from stdin\n"
            "  passcheck --stdin                 # Read one line from stdin\n"
            "  passcheck --batch passwords.txt   # Check passwords in file\n"
        ),
    )
    parser.add_argument("--stdin", action="store_true",
                        help="Read password from stdin")
    parser.add_argument("--batch", metavar="FILE",
                        help="Check passwords from file (one per line)")
    parser.add_argument("--version", action="version",
                        version="passcheck 1.0.0")
    
    args = parser.parse_args()
    
    passwords = []
    
    if args.batch:
        try:
            with open(args.batch) as f:
                passwords = [l.strip() for l in f if l.strip()]
        except FileNotFoundError:
            print(f"Error: File '{args.batch}' not found", file=sys.stderr)
            sys.exit(1)
    elif args.stdin or not sys.stdin.isatty():
        passwords = [sys.stdin.readline().strip()]
    else:
        import getpass
        pwd = getpass.getpass("Enter password to check: ")
        passwords = [pwd]
    
    for pwd in passwords:
        if not pwd:
            continue
        score, grade, ent, issues = analyze(pwd)
        
        print()
        print(f"  {color('█', '36')} Password Analysis")
        print(f"  {color('─' * 40, '90')}")
        print(f"  Length:    {len(pwd)} characters")
        print(f"  Entropy:   {ent:.1f} bits")
        print(f"  Score:     {score}/100  {grade}")
        print()
        
        # Visual bar
        bar_width = 30
        filled = int(score / 100 * bar_width)
        bar = color("█" * filled, "32") if score >= 60 else \
              color("█" * filled, "33") if score >= 40 else \
              color("█" * filled, "31")
        empty = "░" * (bar_width - filled)
        print(f"  [{bar}{empty}]")
        print()
        
        if issues:
            print(f"  {color('Issues:', '33')}")
            for iss in issues:
                print(f"    {color('•', '31')} {iss}")
        else:
            print(f"  {color('✓ No issues found', '32')}")
        print()


if __name__ == "__main__":
    main()