from __future__ import annotations

from dataclasses import dataclass
from email.utils import parseaddr
import logging
from typing import Any

from app.llm_classifier import LLMEmailClassifier

METADATA_HEADERS = [
    "From",
    "Subject",
    "List-Unsubscribe",
    "Precedence",
]

AD_SUBJECT_KEYWORDS = {
    "discount",
    "offer",
    "sale",
    "promo",
    "newsletter",
    "deal",
    "save",
    "coupon",
    "special offer",
    "limited time",
}

AD_SENDER_HINTS = {
    "newsletter",
    "marketing",
    "offers",
    "promotions",
    "deals",
    "no-reply",
    "noreply",
}

logger = logging.getLogger("personal-agent.gmail")


@dataclass(frozen=True)
class ScanResult:
    scanned: int
    linkedin: int
    advertising: int
    skipped: int
    failed: int


class GmailTriageAgent:
    def __init__(
        self,
        gmail_service: Any,
        query: str,
        *,
        classifier: LLMEmailClassifier | None = None,
        fallback_to_rules: bool = True,
    ) -> None:
        self.gmail_service = gmail_service
        self.query = query
        self.classifier = classifier
        self.fallback_to_rules = fallback_to_rules

    def ensure_labels(self) -> dict[str, str]:
        labels_response = (
            self.gmail_service.users().labels().list(userId="me").execute()
        )
        labels = labels_response.get("labels", [])
        label_by_name = {label["name"]: label["id"] for label in labels}

        for required_name in ("LinkedIn", "Advertising", "AgentProcessed"):
            if required_name not in label_by_name:
                created = (
                    self.gmail_service.users()
                    .labels()
                    .create(
                        userId="me",
                        body={
                            "name": required_name,
                            "labelListVisibility": "labelShow",
                            "messageListVisibility": "show",
                        },
                    )
                    .execute()
                )
                label_by_name[required_name] = created["id"]

        return label_by_name

    def scan_and_route_messages(self, max_results: int = 100) -> ScanResult:
        label_by_name = self.ensure_labels()
        inbox_messages = (
            self.gmail_service.users()
            .messages()
            .list(userId="me", q=self.query, maxResults=max_results)
            .execute()
            .get("messages", [])
        )

        linkedin = 0
        advertising = 0
        skipped = 0
        failed = 0

        for message in inbox_messages:
            outcome = self._route_message(message["id"], label_by_name)
            if outcome == "linkedin":
                linkedin += 1
            elif outcome == "advertising":
                advertising += 1
            elif outcome == "skipped":
                skipped += 1
            else:
                failed += 1

        return ScanResult(
            scanned=len(inbox_messages),
            linkedin=linkedin,
            advertising=advertising,
            skipped=skipped,
            failed=failed,
        )

    def _route_message(self, message_id: str, label_by_name: dict[str, str]) -> str:
        try:
            message = (
                self.gmail_service.users()
                .messages()
                .get(
                    userId="me",
                    id=message_id,
                    format="metadata",
                    metadataHeaders=METADATA_HEADERS,
                )
                .execute()
            )
            headers = {
                h["name"].lower(): h["value"]
                for h in message.get("payload", {}).get("headers", [])
            }
            label_ids = set(message.get("labelIds", []))

            sender = headers.get("from", "")
            subject = headers.get("subject", "")
            snippet = message.get("snippet", "")
            list_unsubscribe = headers.get("list-unsubscribe", "")
            precedence = headers.get("precedence", "")

            label = self._classify_email(
                message_id=message_id,
                sender=sender,
                subject=subject,
                snippet=snippet,
                list_unsubscribe=list_unsubscribe,
                precedence=precedence,
                message_label_ids=label_ids,
            )

            add_labels = [label_by_name["AgentProcessed"]]
            remove_labels = []

            if label == "LINKEDIN":
                add_labels.insert(0, label_by_name["LinkedIn"])
                remove_labels.append("INBOX")
                outcome = "linkedin"
            elif label == "ADVERTISING":
                add_labels.insert(0, label_by_name["Advertising"])
                remove_labels.append("INBOX")
                outcome = "advertising"
            else:
                outcome = "skipped"

            (
                self.gmail_service.users()
                .messages()
                .modify(
                    userId="me",
                    id=message_id,
                    body={
                        "addLabelIds": add_labels,
                        "removeLabelIds": remove_labels,
                    },
                )
                .execute()
            )

            return outcome
        except Exception:
            logger.exception("Failed to route message %s", message_id)
            return "failed"

    def _classify_email(
        self,
        *,
        message_id: str,
        sender: str,
        subject: str,
        snippet: str,
        list_unsubscribe: str,
        precedence: str,
        message_label_ids: set[str],
    ) -> str:
        if self.classifier:
            try:
                llm_result = self.classifier.classify(
                    sender=sender,
                    subject=subject,
                    snippet=snippet,
                    list_unsubscribe=list_unsubscribe,
                    precedence=precedence,
                    message_label_ids=message_label_ids,
                )
                logger.info(
                    "Message %s classified by LLM as %s (confidence=%.2f)",
                    message_id,
                    llm_result.label,
                    llm_result.confidence,
                )
                return llm_result.label
            except Exception:
                logger.exception("LLM classification failed for %s", message_id)
                if not self.fallback_to_rules:
                    return "OTHER"

        if self.fallback_to_rules:
            if self._is_linkedin_email(sender=sender, subject=subject):
                return "LINKEDIN"
            if self._is_advertising_email(
                sender=sender,
                subject=subject,
                list_unsubscribe=list_unsubscribe,
                precedence=precedence,
                message_label_ids=message_label_ids,
            ):
                return "ADVERTISING"

        return "OTHER"

    def _is_linkedin_email(self, sender: str, subject: str) -> bool:
        sender_lower = sender.lower()
        subject_lower = subject.lower()

        if "linkedin" in sender_lower or "linkedin" in subject_lower:
            return True

        parsed_address = parseaddr(sender)[1].lower()
        return parsed_address.endswith("@linkedin.com")

    def _is_advertising_email(
        self,
        sender: str,
        subject: str,
        list_unsubscribe: str,
        precedence: str,
        message_label_ids: set[str],
    ) -> bool:
        sender_lower = sender.lower()
        subject_lower = subject.lower()
        precedence_lower = precedence.lower()

        if "CATEGORY_PROMOTIONS" in message_label_ids:
            return True

        if list_unsubscribe.strip():
            return True

        if precedence_lower in {"bulk", "list", "junk"}:
            return True

        if any(keyword in subject_lower for keyword in AD_SUBJECT_KEYWORDS):
            return True

        return any(hint in sender_lower for hint in AD_SENDER_HINTS)