import os
import sys
import requests
from datetime import datetime, timedelta, timezone

def main():
    """
    Main function to fetch pull requests from a Gitea repository and process them.
    """
    # --- Get configuration from environment variables ---
    try:
        instance_url = os.environ['INSTANCE_URL'].rstrip('/')
        repository = os.environ['REPOSITORY']
        token = os.environ['TOKEN']
        stale_days = int(os.environ.get('STALE_DAYS'))
        stale_tag = int(os.environ.get('STALE_TAG'))
        exclude_tag = int(os.environ.get('EXCLUDE_TAG'))
        required_tag = int(os.environ.get('REQUIRED_TAG'))
    except KeyError as e:
        print(f"Error: Missing required environment variable: {e}", file=sys.stderr)
        sys.exit(1)

    print(f">> Processing pull requests ...")


    # --- Switch off checks if env is empty ---
    if required_tag == None:
        enable_required_tag = False
        print(f">> No optional required tag set.")
    else:
        enable_required_tag = True

    if exclude_tag == None:
        enable_exclude_tag= False
        print(f">> No optional exclusive tag set.")
    else:
        enable_exclude_tag = True

    if stale_days == None:
        enable_stale_tag= False
        print(f">> No value for stale days.")
    else:
        older_than_date = datetime.now(timezone.utc) - timedelta(days=stale_days)
        enable_stale_tag = True


    # --- Check if any actions are enabled ---
    if not any([enable_stale_tag]) == True:
        print(f">> No actions enabled, exiting.")
        sys.exit(1)


    # --- Set up API headers and base URL ---
    headers = {
        'Authorization': f'token {token}',
        'Accept': 'application/json',
        'Content-Type': 'application/json'
    }
    base_api_url = f"{instance_url}/api/v1/repos/{repository}/pulls"
    params = {'state': 'open'}


    # --- Fetch pull requests ---
    print(">> Fetching pull requests ...")
    try:
        response = requests.get(base_api_url, headers=headers, params=params, timeout=30)
        response.raise_for_status()
        pull_requests = response.json()
    except requests.exceptions.RequestException as e:
        print(f"Error fetching pull requests: {e}", file=sys.stderr)
        sys.exit(1)

    if not pull_requests:
        print(">> No open pull requests found, exiting.")
        sys.exit(0)

    print(f">> Processing {len(pull_requests)} open pull requests ...")


    # --- Process Pull Requests ---
    for pr in pull_requests:
        pr_number = pr['number']
        pr_created_at = datetime.fromisoformat(pr['created_at'].replace('Z', '+00:00'))


        # -- Process labels ---
        pr_current_labels = {label['name'] for label in pr.get('labels', [])}
        update_labels = pr_current_labels

        if enable_required_tag:
            if not required_tag in pr_current_labels:
                print(f">> Skipping PR #{pr_number} because it does not have the '{required_tag}' tag.")
                continue

        if enable_exclude_tag:
            if exclude_tag in pr_current_labels:
                print(f">> Skipping PR #{pr_number} because it has the '{exclude_tag}' tag.")
                continue

        if enable_stale_tag:
            if pr_created_at < older_than_date:
                if stale_tag in pr_current_labels:
                    print(f">> Skipping issue #{pr_number} because it already has the '{stale_tag}' tag.")
                    continue

                print(f">> Will tag PR #{pr_number} with '{stale_tag}'")
                update_labels.add(stale_tag)


        # --- Make update with new labels ---
        update_payload = {'labels': list(update_labels)}
        update_url = f"{base_api_url}/{pr_number}/labels"

        print(f">> Updating PR #{pr_number} ...")
        try:
            update_response = requests.put(update_url, headers=headers, json=update_payload, timeout=30)
            update_response.raise_for_status()
            print(f">> Successfully updated labels for PR #{pr_number}")
        except requests.exceptions.RequestException as e:
            print(f"Error updating labels for PR #{pr_number}: {e}", file=sys.stderr)

    print(">> Finished processing pull requests.")

if __name__ == "__main__":
    main()