import base64
import email
from enum import Enum
from typing import Any, Dict, List, Optional, Type

from pydantic import BaseModel, Field

from langchain.callbacks.manager import CallbackManagerForToolRun
from langchain.tools.gmail.base import GmailBaseTool
from langchain.tools.gmail.utils import clean_email_body


class Resource(str, Enum):
    """Enumerator of Resources to search."""

    THREADS = "threads"
    MESSAGES = "messages"


class SearchArgsSchema(BaseModel):
    """Input for SearchGmailTool."""

    # From https://support.google.com/mail/answer/7190?hl=en
    query: str = Field(
        ...,
        description="The Gmail query. Example filters include from:sender,"
        " to:recipient, subject:subject, -filtered_term,"
        " in:folder, is:important|read|starred, after:year/mo/date, "
        "before:year/mo/date, label:label_name"
        ' "exact phrase".'
        " Search newer/older than using d (day), m (month), and y (year): "
        "newer_than:2d, older_than:1y."
        " Attachments with extension example: filename:pdf. Multiple term"
        " matching example: from:amy OR from:david.",
    )
    resource: Resource = Field(
        default=Resource.MESSAGES,
        description="Whether to search for threads or messages.",
    )
    max_results: int = Field(
        default=10,
        description="The maximum number of results to return.",
    )


class GmailSearch(GmailBaseTool):
    """Tool that searches for messages or threads in Gmail."""

    name: str = "search_gmail"
    description: str = (
        "Use this tool to search for email messages or threads."
        " The input must be a valid Gmail query."
        " The output is a JSON list of the requested resource."
    )
    args_schema: Type[SearchArgsSchema] = SearchArgsSchema

    def _parse_threads(self, threads: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
        # Add the thread message snippets to the thread results
        results = []
        for thread in threads:
            thread_id = thread["id"]
            thread_data = (
                self.api_resource.users()
                .threads()
                .get(userId="me", id=thread_id)
                .execute()
            )
            messages = thread_data["messages"]
            thread["messages"] = []
            for message in messages:
                snippet = message["snippet"]
                thread["messages"].append({"snippet": snippet, "id": message["id"]})
            results.append(thread)

        return results

    def _parse_messages(self, messages: List[Dict[str, Any]]) -> List[Dict[str, Any]]:
        results = []
        for message in messages:
            message_id = message["id"]
            message_data = (
                self.api_resource.users()
                .messages()
                .get(userId="me", format="raw", id=message_id)
                .execute()
            )

            raw_message = base64.urlsafe_b64decode(message_data["raw"])

            email_msg = email.message_from_bytes(raw_message)

            subject = email_msg["Subject"]
            sender = email_msg["From"]

            message_body = email_msg.get_payload()

            body = clean_email_body(message_body)

            results.append(
                {
                    "id": message["id"],
                    "threadId": message_data["threadId"],
                    "snippet": message_data["snippet"],
                    "body": body,
                    "subject": subject,
                    "sender": sender,
                }
            )
        return results

    def _run(
        self,
        query: str,
        resource: Resource = Resource.MESSAGES,
        max_results: int = 10,
        run_manager: Optional[CallbackManagerForToolRun] = None,
    ) -> List[Dict[str, Any]]:
        """Run the tool."""
        results = (
            self.api_resource.users()
            .messages()
            .list(userId="me", q=query, maxResults=max_results)
            .execute()
            .get(resource.value, [])
        )
        if resource == Resource.THREADS:
            return self._parse_threads(results)
        elif resource == Resource.MESSAGES:
            return self._parse_messages(results)
        else:
            raise NotImplementedError(f"Resource of type {resource} not implemented.")
