"""Password policy validation and enforcement."""

import re
from typing import List, Optional
from dataclasses import dataclass
from sqlalchemy.orm import Session

from app import crud


@dataclass
class PasswordPolicy:
    """Password policy configuration."""
    min_length: int = 8
    max_length: int = 128
    require_uppercase: bool = True
    require_lowercase: bool = True
    require_digit: bool = True
    require_special: bool = False
    special_characters: str = "!@#$%^&*()_+-=[]{}|;:,.<>?"
    disallow_username: bool = True
    disallow_email: bool = True
    disallow_common: bool = True


# Common passwords to disallow
COMMON_PASSWORDS = {
    "password", "123456", "12345678", "qwerty", "abc123",
    "monkey", "1234567", "letmein", "trustno1", "dragon",
    "baseball", "iloveyou", "master", "sunshine", "ashley",
    "bailey", "passw0rd", "shadow", "123123", "654321",
    "superman", "qazwsx", "michael", "football", "password1",
    "password123", "welcome", "jesus", "ninja", "mustang",
    "admin", "admin123", "root", "toor", "administrator"
}


def get_password_policy(db: Optional[Session] = None) -> PasswordPolicy:
    """Get password policy from settings or use defaults."""
    policy = PasswordPolicy()

    if db:
        try:
            # Load settings from database
            min_length = crud.settings.get_setting_value(db, "password_min_length")
            if min_length is not None:
                policy.min_length = int(min_length)

            require_uppercase = crud.settings.get_setting_value(db, "password_require_uppercase")
            if require_uppercase is not None:
                policy.require_uppercase = str(require_uppercase).lower() in ("true", "1")

            require_lowercase = crud.settings.get_setting_value(db, "password_require_lowercase")
            if require_lowercase is not None:
                policy.require_lowercase = str(require_lowercase).lower() in ("true", "1")

            require_digit = crud.settings.get_setting_value(db, "password_require_digit")
            if require_digit is not None:
                policy.require_digit = str(require_digit).lower() in ("true", "1")

            require_special = crud.settings.get_setting_value(db, "password_require_special")
            if require_special is not None:
                policy.require_special = str(require_special).lower() in ("true", "1")

        except Exception:
            pass  # Use defaults on error

    return policy


def validate_password(
    password: str,
    policy: Optional[PasswordPolicy] = None,
    username: Optional[str] = None,
    email: Optional[str] = None
) -> List[str]:
    """
    Validate password against policy.
    Returns list of validation errors (empty list if valid).
    """
    if policy is None:
        policy = PasswordPolicy()

    errors = []

    # Length checks
    if len(password) < policy.min_length:
        errors.append(f"Password must be at least {policy.min_length} characters long")

    if len(password) > policy.max_length:
        errors.append(f"Password must not exceed {policy.max_length} characters")

    # Character requirements
    if policy.require_uppercase and not re.search(r"[A-Z]", password):
        errors.append("Password must contain at least one uppercase letter")

    if policy.require_lowercase and not re.search(r"[a-z]", password):
        errors.append("Password must contain at least one lowercase letter")

    if policy.require_digit and not re.search(r"\d", password):
        errors.append("Password must contain at least one digit")

    if policy.require_special:
        special_pattern = f"[{re.escape(policy.special_characters)}]"
        if not re.search(special_pattern, password):
            errors.append("Password must contain at least one special character")

    # Disallow username/email in password
    password_lower = password.lower()

    if policy.disallow_username and username:
        if username.lower() in password_lower:
            errors.append("Password must not contain your username")

    if policy.disallow_email and email:
        email_parts = email.lower().split("@")
        if email_parts[0] in password_lower:
            errors.append("Password must not contain your email address")

    # Disallow common passwords
    if policy.disallow_common:
        if password_lower in COMMON_PASSWORDS:
            errors.append("Password is too common. Please choose a stronger password")

    return errors


def get_password_requirements(policy: Optional[PasswordPolicy] = None) -> dict:
    """Get password requirements as a dictionary (for frontend display)."""
    if policy is None:
        policy = PasswordPolicy()

    requirements = {
        "min_length": policy.min_length,
        "max_length": policy.max_length,
        "require_uppercase": policy.require_uppercase,
        "require_lowercase": policy.require_lowercase,
        "require_digit": policy.require_digit,
        "require_special": policy.require_special,
    }

    # Generate human-readable description
    rules = [f"At least {policy.min_length} characters"]

    if policy.require_uppercase:
        rules.append("At least one uppercase letter (A-Z)")
    if policy.require_lowercase:
        rules.append("At least one lowercase letter (a-z)")
    if policy.require_digit:
        rules.append("At least one digit (0-9)")
    if policy.require_special:
        rules.append(f"At least one special character ({policy.special_characters[:10]}...)")

    requirements["rules"] = rules

    return requirements


def check_password_strength(password: str) -> dict:
    """
    Check password strength and return a score.
    Returns dict with score (0-100), level (weak/medium/strong/very_strong), and feedback.
    """
    score = 0
    feedback = []

    # Length scoring
    length = len(password)
    if length >= 8:
        score += 20
    if length >= 12:
        score += 10
    if length >= 16:
        score += 10

    # Character variety scoring
    has_upper = bool(re.search(r"[A-Z]", password))
    has_lower = bool(re.search(r"[a-z]", password))
    has_digit = bool(re.search(r"\d", password))
    has_special = bool(re.search(r"[!@#$%^&*()_+\-=\[\]{}|;:,.<>?]", password))

    if has_upper:
        score += 15
    if has_lower:
        score += 15
    if has_digit:
        score += 15
    if has_special:
        score += 15

    # Bonus for mixing character types
    variety = sum([has_upper, has_lower, has_digit, has_special])
    if variety >= 3:
        score += 10
    if variety == 4:
        score += 10

    # Penalties
    if password.lower() in COMMON_PASSWORDS:
        score = min(score, 20)
        feedback.append("This is a commonly used password")

    if re.search(r"(.)\1{2,}", password):
        score -= 10
        feedback.append("Avoid repeated characters")

    if re.search(r"(012|123|234|345|456|567|678|789|890|abc|bcd|cde|def)", password.lower()):
        score -= 10
        feedback.append("Avoid sequential characters")

    # Ensure score is in valid range
    score = max(0, min(100, score))

    # Determine strength level
    if score >= 80:
        level = "very_strong"
    elif score >= 60:
        level = "strong"
    elif score >= 40:
        level = "medium"
    else:
        level = "weak"

    # Add suggestions
    if not has_upper:
        feedback.append("Add uppercase letters")
    if not has_lower:
        feedback.append("Add lowercase letters")
    if not has_digit:
        feedback.append("Add numbers")
    if not has_special:
        feedback.append("Add special characters")
    if length < 12:
        feedback.append("Use a longer password")

    return {
        "score": score,
        "level": level,
        "feedback": feedback[:3]  # Limit to top 3 suggestions
    }