"""Input validation with proper error raising."""
import re
from typing import Optional
from .errors import ValidationError


def validate_grant_id(gid: str) -> str:
    """
    Validate and normalize grant ID.

    Args:
        gid: Grant ID in any format ("2315", "competition-2315", etc.)

    Returns:
        Normalized ID (just the numeric part without prefix)

    Raises:
        ValidationError: If ID format is invalid

    Example:
        >>> validate_grant_id("2315")
        '2315'
        >>> validate_grant_id("competition-2315")
        '2315'
        >>> validate_grant_id("invalid")
        ValidationError: Invalid grant ID format: 'invalid'
    """
    if not gid:
        raise ValidationError("Grant ID cannot be empty")

    gid = str(gid).strip()

    # Extract numeric part
    match = re.match(r'^(?:comp(?:etition)?-|grant-)?(\d{3,7})$', gid, re.I)
    if not match:
        raise ValidationError(
            f"Invalid grant ID format: '{gid}'. "
            f"Expected: '2315' or 'competition-2315'"
        )

    numeric_id = match.group(1)
    return numeric_id


def validate_url(url: str, *, allowed_hosts: Optional[set] = None) -> str:
    """
    Validate URL and check against allowlist.

    Args:
        url: URL to validate
        allowed_hosts: Optional set of allowed hostnames

    Returns:
        Validated URL (unchanged)

    Raises:
        ValidationError: If URL is invalid or not allowed
    """
    from urllib.parse import urlparse

    if not url:
        raise ValidationError("URL cannot be empty")

    url = str(url).strip()

    if not url.startswith(('http://', 'https://')):
        raise ValidationError(
            f"URL must start with http:// or https://: {url}"
        )

    try:
        parsed = urlparse(url)
    except Exception as e:
        raise ValidationError(f"Malformed URL: {url}") from e

    if not parsed.netloc:
        raise ValidationError(f"URL has no hostname: {url}")

    if allowed_hosts and parsed.netloc not in allowed_hosts:
        allowed_preview = ', '.join(list(allowed_hosts)[:3])
        raise ValidationError(
            f"URL host '{parsed.netloc}' not in allowlist. "
            f"Allowed: {allowed_preview}..."
        )

    return url


def sanitize_filename(name: str, max_length: int = 200) -> str:
    """
    Sanitize filename to prevent path traversal.

    Args:
        name: Original filename
        max_length: Maximum length

    Returns:
        Safe filename

    Example:
        >>> sanitize_filename("../../../etc/passwd")
        'etc_passwd'
    """
    if not name:
        raise ValidationError("Filename cannot be empty")

    # Remove path separators and dangerous chars
    safe = re.sub(r'[^\w\-.]', '_', str(name))
    safe = safe.strip('._')

    if not safe:
        raise ValidationError(f"Filename '{name}' produces empty result after sanitization")

    return safe[:max_length]


def validate_search_query(query: str, max_length: int = 500) -> str:
    """
    Validate search query.

    Args:
        query: Search query string
        max_length: Maximum allowed length

    Returns:
        Validated query (stripped)

    Raises:
        ValidationError: If query is empty or too long
    """
    if not query:
        raise ValidationError("Search query cannot be empty")

    query = str(query).strip()

    if not query:
        raise ValidationError("Search query cannot be whitespace only")

    if len(query) > max_length:
        raise ValidationError(
            f"Search query too long ({len(query)} chars, max {max_length})"
        )

    return query


def validate_positive_int(value: any, name: str = "value") -> int:
    """
    Validate positive integer.

    Args:
        value: Value to validate
        name: Name of parameter (for error messages)

    Returns:
        Validated integer

    Raises:
        ValidationError: If not a positive integer
    """
    try:
        val = int(value)
    except (TypeError, ValueError) as e:
        raise ValidationError(f"{name} must be an integer, got {type(value).__name__}") from e

    if val <= 0:
        raise ValidationError(f"{name} must be positive, got {val}")

    return val


def validate_date_string(date_str: str, name: str = "date") -> str:
    """
    Validate ISO date string (YYYY-MM-DD).

    Args:
        date_str: Date string to validate
        name: Name of parameter (for error messages)

    Returns:
        Validated date string

    Raises:
        ValidationError: If not valid ISO date format
    """
    if not date_str:
        raise ValidationError(f"{name} cannot be empty")

    date_str = str(date_str).strip()

    # Check format
    if not re.match(r'^\d{4}-\d{2}-\d{2}$', date_str):
        raise ValidationError(
            f"{name} must be in YYYY-MM-DD format, got: {date_str}"
        )

    # Validate actual date (catches invalid like 2025-13-45)
    try:
        from datetime import datetime
        datetime.strptime(date_str, '%Y-%m-%d')
    except ValueError as e:
        raise ValidationError(f"Invalid date: {date_str}") from e

    return date_str