"""Shared utility functions for ai-chat-exporter."""

import re
from datetime import datetime, timezone
from pathlib import Path

from slugify import slugify


# Keys whose values should be redacted in log output
_SENSITIVE_KEYS = frozenset(
    {"token", "key", "secret", "password", "authorization", "session", "sessionkey"}
)


def generate_filename(title: str, conv_id: str, created_at: str) -> str:
    """Build the export filename for a conversation.

    Format: YYYY-MM-DD_{slug}_{id[:8]}.md

    Args:
        title: Conversation title.
        conv_id: Conversation ID (at least 8 chars recommended).
        created_at: ISO8601 creation timestamp.

    Returns:
        Filename string, e.g. "2024-06-10_my-conversation_abc12345.md"
    """
    dt = _parse_dt(created_at)
    date_str = dt.strftime("%Y-%m-%d")
    slug = slugify(title, max_length=60, word_boundary=True) or "untitled"
    short_id = conv_id[:8]
    return f"{date_str}_{slug}_{short_id}.md"


def build_export_path(
    base_dir: Path,
    provider: str,
    project: str | None,
    created_at: str,
    filename: str,
    structure: str = "provider/project/year",
) -> Path:
    """Build the full output path for an exported file.

    Args:
        base_dir: Root export directory (e.g. Path("./exports")).
        provider: "chatgpt" or "claude".
        project: Project name (will be slugified), or None/empty for no-project.
        created_at: ISO8601 creation timestamp (used for year folder).
        filename: Already-generated filename from generate_filename().
        structure: OUTPUT_STRUCTURE value. One of:
            "provider/project/year" (default)
            "provider/project"
            "provider/year"

    Returns:
        Full Path to the output file.
    """
    dt = _parse_dt(created_at)
    year = str(dt.year)
    project_slug = slugify(project, max_length=60, word_boundary=True) if project else "no-project"

    parts: list[str] = [provider]

    if structure == "provider/project/year":
        parts += [project_slug, year]
    elif structure == "provider/project":
        parts += [project_slug]
    elif structure == "provider/year":
        parts += [year]
    else:
        # Unknown structure — fall back to default
        parts += [project_slug, year]

    return base_dir.joinpath(*parts) / filename


def redact_secrets(data: object) -> object:
    """Recursively redact sensitive values from a dict/list for safe logging.

    Keys matching _SENSITIVE_KEYS (case-insensitive) have their values
    replaced with "[REDACTED]".

    Args:
        data: Any JSON-serializable object.

    Returns:
        A new object with sensitive values replaced.
    """
    if isinstance(data, dict):
        return {
            k: "[REDACTED]" if k.lower() in _SENSITIVE_KEYS else redact_secrets(v)
            for k, v in data.items()
        }
    if isinstance(data, list):
        return [redact_secrets(item) for item in data]
    return data


def format_token_status(token: str | None, expiry_dt: datetime | None = None) -> str:
    """Format a token for the startup config summary log line.

    Never includes the actual token value.

    Args:
        token: The token string, or None/empty if not set.
        expiry_dt: Decoded expiry datetime (for JWTs). None if unknown.

    Returns:
        Human-readable status, e.g. "[SET - expires in 3 days]" or "[NOT SET]"
    """
    if not token:
        return "[NOT SET]"

    if expiry_dt is None:
        return "[SET]"

    now = datetime.now(tz=timezone.utc)
    if expiry_dt.tzinfo is None:
        expiry_dt = expiry_dt.replace(tzinfo=timezone.utc)

    delta = expiry_dt - now
    days = delta.days

    if days < 0:
        return "[SET - EXPIRED]"
    if days == 0:
        hours = int(delta.seconds / 3600)
        return f"[SET - expires in {hours}h]"
    return f"[SET - expires in {days} day{'s' if days != 1 else ''}]"


def _parse_dt(ts: str) -> datetime:
    """Parse an ISO8601 timestamp to a datetime object.

    Handles both timezone-aware and naive strings.
    """
    ts = ts.rstrip("Z")
    # Remove sub-second precision beyond microseconds
    ts = re.sub(r"(\.\d{6})\d+", r"\1", ts)
    try:
        dt = datetime.fromisoformat(ts)
    except ValueError:
        # Fallback: try common formats
        for fmt in ("%Y-%m-%dT%H:%M:%S", "%Y-%m-%d"):
            try:
                dt = datetime.strptime(ts, fmt)
                break
            except ValueError:
                continue
        else:
            dt = datetime.now()

    if dt.tzinfo is None:
        dt = dt.replace(tzinfo=timezone.utc)
    return dt