"""Utility functions for Gmail/Calendar tools."""

import base64
import mimetypes
import re
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email import encoders
from html.parser import HTMLParser
from pathlib import Path
from typing import Dict, List, Optional


class HTMLToText(HTMLParser):
    """Convert HTML to plain text."""

    def __init__(self):
        super().__init__()
        self.text = []
        self.skip = False

    def handle_data(self, data):
        if not self.skip:
            self.text.append(data)

    def handle_starttag(self, tag, attrs):
        if tag in ["script", "style"]:
            self.skip = True
        elif tag == "br":
            self.text.append("\n")
        elif tag == "p":
            self.text.append("\n\n")

    def handle_endtag(self, tag):
        if tag in ["script", "style"]:
            self.skip = False
        elif tag in ["p", "div"]:
            self.text.append("\n")

    def get_text(self):
        return "".join(self.text).strip()


def html_to_text(html: str) -> str:
    """Convert HTML to plain text.

    Args:
        html: HTML content

    Returns:
        Plain text content
    """
    parser = HTMLToText()
    parser.feed(html)
    return parser.get_text()


def create_mime_message(
    to: str,
    subject: str,
    body: str,
    from_email: str = "me",
    cc: Optional[List[str]] = None,
    reply_to_message_id: Optional[str] = None,
    attachments: Optional[List[str]] = None,
) -> Dict:
    """Create a MIME message for Gmail API.

    Args:
        to: Recipient email address
        subject: Email subject
        body: Email body (plain text or HTML)
        from_email: Sender email (default: "me")
        cc: Optional list of CC recipients
        reply_to_message_id: Optional message ID to reply to
        attachments: Optional list of file paths to attach

    Returns:
        Dict with 'raw' key containing base64url-encoded message
    """
    is_html = bool(re.search(r"<[a-z][\s\S]*>", body, re.IGNORECASE))

    # Build the body part first
    if attachments:
        # mixed wraps body alternative + file parts
        message = MIMEMultipart("mixed")
        body_part = MIMEMultipart("alternative")
    else:
        message = MIMEMultipart("alternative")
        body_part = message

    message["To"] = to
    message["From"] = from_email
    message["Subject"] = subject

    if cc:
        message["Cc"] = ", ".join(cc)

    if reply_to_message_id:
        message["In-Reply-To"] = reply_to_message_id
        message["References"] = reply_to_message_id

    if is_html:
        body_part.attach(MIMEText(html_to_text(body), "plain"))
        body_part.attach(MIMEText(body, "html"))
    else:
        body_part.attach(MIMEText(body, "plain"))

    if attachments:
        message.attach(body_part)
        for file_path in attachments:
            path = Path(file_path)
            mime_type, _ = mimetypes.guess_type(str(path))
            main_type, sub_type = (mime_type or "application/octet-stream").split("/", 1)
            with open(path, "rb") as f:
                part = MIMEBase(main_type, sub_type)
                part.set_payload(f.read())
            encoders.encode_base64(part)
            part.add_header("Content-Disposition", "attachment", filename=path.name)
            message.attach(part)

    raw_message = base64.urlsafe_b64encode(message.as_bytes()).decode()
    return {"raw": raw_message}


def parse_email_message(message: Dict) -> Dict:
    """Parse Gmail API message into readable format.

    Args:
        message: Gmail API message object

    Returns:
        Dict with parsed fields: from, to, subject, date, body, snippet
    """
    headers = {
        h["name"].lower(): h["value"]
        for h in message.get("payload", {}).get("headers", [])
    }

    result = {
        "id": message.get("id"),
        "thread_id": message.get("threadId"),
        "from": headers.get("from", ""),
        "to": headers.get("to", ""),
        "cc": headers.get("cc", ""),
        "subject": headers.get("subject", ""),
        "date": headers.get("date", ""),
        "snippet": message.get("snippet", ""),
        "labels": message.get("labelIds", []),
    }

    return result


def get_email_body(message: Dict) -> str:
    """Extract email body from Gmail API message.

    Args:
        message: Gmail API message object

    Returns:
        Email body as plain text
    """
    payload = message.get("payload", {})

    def get_body_from_part(part: Dict) -> Optional[str]:
        """Recursively extract body from MIME parts."""
        mime_type = part.get("mimeType", "")
        body_data = part.get("body", {}).get("data")

        if body_data:
            decoded = base64.urlsafe_b64decode(body_data).decode("utf-8", errors="ignore")
            if mime_type == "text/html":
                return html_to_text(decoded)
            elif mime_type == "text/plain":
                return decoded

        # Check nested parts
        for subpart in part.get("parts", []):
            result = get_body_from_part(subpart)
            if result:
                return result

        return None

    # Try to get body
    body = get_body_from_part(payload)

    if not body:
        # Fallback to snippet
        body = message.get("snippet", "")

    return body


def format_email_summary(emails: List[Dict], include_body: bool = False) -> str:
    """Format emails into a readable summary.

    Args:
        emails: List of parsed email dicts
        include_body: Whether to include full body

    Returns:
        Formatted string summary
    """
    if not emails:
        return "No emails found."

    lines = []
    for i, email_data in enumerate(emails, 1):
        lines.append(f"{i}. From: {email_data['from']}")
        lines.append(f"   Subject: {email_data['subject']}")
        lines.append(f"   Date: {email_data['date']}")
        lines.append(f"   Message-ID: {email_data.get('id', 'N/A')}")

        if include_body and "body" in email_data:
            # Truncate long bodies
            body = email_data["body"]
            if len(body) > 2000:
                body = body[:2000] + "..."
            lines.append(f"   Body: {body}")
        else:
            lines.append(f"   Snippet: {email_data['snippet']}")

        lines.append("")  # Blank line

    return "\n".join(lines)