import os
import sys
import json
import requests
from datetime import datetime, timedelta
from todoist_api_python.api import TodoistAPI
from jinja2 import Environment, FileSystemLoader, select_autoescape

ATTACHMENTS_DIR = "attachments"


def usage():
    print("""
    Todoist Export Script
    ---------------------
    Exports all active and completed tasks from the Todoist API to a JSON file, including attachments and comments, and generates a human-readable HTML backup using Jinja2.

    Usage:
      python export_todoist.py export
        - Exports all data and generates JSON and HTML files.
      python export_todoist.py [any other argument or none]
        - Shows this help message.
    """)


def get_api_key():
    key = os.environ.get("TODOIST_KEY")
    if not key:
        print("Error: TODOIST_KEY environment variable not set.")
        sys.exit(1)
    return key


def ensure_attachments_dir():
    if not os.path.exists(ATTACHMENTS_DIR):
        os.makedirs(ATTACHMENTS_DIR)


def download_attachment(url, filename):
    local_path = os.path.join(ATTACHMENTS_DIR, filename)
    if os.path.exists(local_path):
        return local_path
    print(f"Downloading attachment {url}")
    r = requests.get(url, stream=True)
    if r.status_code == 200:
        with open(local_path, 'wb') as f:
            for chunk in r.iter_content(1024):
                f.write(chunk)
        return local_path
    else:
        return None


def fetch_all_projects(api):
    ret = []
    projects_iter = api.get_projects()
    for projects in projects_iter:
        for project in projects:
            name = getattr(project, 'name', None)
            id = getattr(project, 'id', None)
            print(f"Found project {name} with ID {id}")
            ret.append(project)
    return ret

def fetch_all_completed_tasks(api, project_id):
    # Fetch all completed tasks for a project using get_completed_tasks_by_completion_date
    # The API only allows up to 3 months per call, so we fetch just once for the last 3 months
    all_completed = []
    since = (datetime.now() - timedelta(days=90)).replace(hour=0, minute=0, second=0, microsecond=0)
    until = datetime.now()
    try:
        completed_iter = api.get_completed_tasks_by_completion_date(since=since, until=until)
        for completed_list in completed_iter:
            for task in completed_list:
                if hasattr(task, 'project_id') and str(task.project_id) == str(project_id):
                    all_completed.append(task)
    except Exception as e:
        print(f"Error fetching completed tasks for {since} to {until}: {e}")
    print(f"Found {len(all_completed)} completed tasks for project {project_id}")
    return all_completed

def fetch_all_tasks(api, project_id, completed=False):
    if completed:
        return fetch_all_completed_tasks(api, project_id)
    else:
        tasks = []
        try:
            tasks_iter = api.get_tasks(project_id=project_id)
            for batch in tasks_iter:
                for task in batch:
                    tasks.append(task)
        except Exception as e:
            print(f"Error fetching active tasks for project {project_id}: {e}")
        print(f"Found {len(tasks)} completed tasks for project {project_id}")
        return tasks


def fetch_comments(api, task_id):
    comments = []
    try:
        comments_iter = api.get_comments(task_id=task_id)
        for batch in comments_iter:
            for comment in batch:
                comments.append(comment)
    except Exception:
        return []
    return comments


def process_task(api, task, completed=False):
    task_dict = task.__dict__.copy()
    # Attachments (if any)
    attachments = []
    if hasattr(task, 'attachments') and task.attachments:
        for att in task.attachments:
            att_dict = att.__dict__.copy()
            if 'file_url' in att_dict and att_dict['file_url']:
                filename = att_dict.get('file_name') or os.path.basename(att_dict['file_url'])
                local_path = download_attachment(att_dict['file_url'], filename)
                if local_path:
                    att_dict['local_file'] = os.path.relpath(local_path)
            attachments.append(att_dict)
    if attachments:
        task_dict['attachments'] = attachments
    # Comments
    comments = fetch_comments(api, task.id)
    if comments:
        task_dict['comments'] = [c.__dict__ for c in comments]
    return task_dict


def main():
    if len(sys.argv) != 2 or sys.argv[1] != "export":
        usage()
        return
    ensure_attachments_dir()
    api = TodoistAPI(get_api_key())
    projects = fetch_all_projects(api)
    data = []
    for project in projects:
        project_dict = project.__dict__.copy()
        project_id = project.id
        # Active tasks
        active_tasks = fetch_all_tasks(api, project_id, completed=False)
        # Completed tasks
        completed_tasks = fetch_all_tasks(api, project_id, completed=True)
        project_dict['tasks'] = [process_task(api, t, completed=False) for t in active_tasks]
        project_dict['completed_tasks'] = [process_task(api, t, completed=True) for t in completed_tasks]
        data.append(project_dict)
    # Write JSON
    today = datetime.now().strftime("%Y-%m-%d")
    json_filename = f"Todoist-Actual-Backup-{today}.json"
    def json_serial(obj):
        if isinstance(obj, datetime):
            return obj.isoformat()
        return str(obj)
    with open(json_filename, "w", encoding="utf-8") as f:
        json.dump(data, f, ensure_ascii=False, indent=2, default=json_serial)
    print(f"Exported data to {json_filename}")
    # Write HTML
    env = Environment(
        loader=FileSystemLoader(os.path.dirname(__file__)),
        autoescape=select_autoescape(['html', 'xml'])
    )
    template = env.get_template("todoist_backup_template.html")
    html_filename = f"Todoist-Actual-Backup-{today}.html"
    with open(html_filename, "w", encoding="utf-8") as f:
        f.write(template.render(projects=data, date=today))
    print(f"Generated HTML backup at {html_filename}")

if __name__ == "__main__":
    main()