from pydantic import BaseModel, Field
from langchain_core.messages import HumanMessage
from src.rag.models import ModelConfigurator as modconf
from src.rag.prompts import PromptConfigurator as promptconf

from src.utils.logging import get_logger

logger = get_logger('lang_detector')

# Common short words for quick language detection (no LLM needed)
SHORT_WORDS_DE = {
    'ja', 'nein', 'danke', 'bitte', 'ok', 'gut', 'hallo', 'hi', 'hey',
    'genau', 'stimmt', 'klar', 'super', 'prima', 'toll', 'schön',
    'mehr', 'weniger', 'was', 'wie', 'wo', 'wann', 'warum', 'wer',
    'und', 'oder', 'aber', 'doch', 'noch', 'schon', 'jetzt', 'hier',
    'gerne', 'natürlich', 'sicher', 'vielleicht', 'also', 'ach', 'aha',
}
SHORT_WORDS_EN = {
    'yes', 'no', 'thanks', 'please', 'ok', 'okay', 'good', 'hello', 'hi', 'hey',
    'right', 'sure', 'great', 'nice', 'cool', 'fine', 'perfect',
    'more', 'less', 'what', 'how', 'where', 'when', 'why', 'who',
    'and', 'or', 'but', 'yet', 'now', 'here', 'there',
    'maybe', 'probably', 'definitely', 'certainly', 'alright',
}

# Patterns for explicit language switch requests
SWITCH_TO_EN_PATTERNS = [
    'in english', 'to english', 'switch to english', 'continue in english',
    'speak english', 'english please', 'prefer english', 'rather in english',
    'answer in english', 'respond in english', 'information in english',
]
SWITCH_TO_DE_PATTERNS = [
    'auf deutsch', 'zu deutsch', 'in deutsch', 'deutsch bitte', 'lieber deutsch',
    'bitte deutsch', 'weiter auf deutsch', 'antworten auf deutsch',
    'in german', 'to german', 'switch to german', 'continue in german',
    'speak german', 'german please', 'prefer german',
]


class LanguageDetectionResult(BaseModel):
    language_code: str = Field(description="ISO language code (e.g., en, de, fa, ru) of the language in which the message is written")


class LanguageDetector:
    def __init__(self) -> None:
        self._model = modconf.get_language_detector_model()
        self._model = self._model.with_structured_output(LanguageDetectionResult)

    def detect_explicit_switch_request(self, query: str) -> str | None:
        """
        Detect if user explicitly requests a language switch.
        Returns 'en', 'de', or None if no explicit switch requested.
        """
        query_lower = query.lower()

        for pattern in SWITCH_TO_EN_PATTERNS:
            if pattern in query_lower:
                logger.info(f"Explicit language switch request detected: -> English")
                return 'en'

        for pattern in SWITCH_TO_DE_PATTERNS:
            if pattern in query_lower:
                logger.info(f"Explicit language switch request detected: -> German")
                return 'de'

        return None

    def _quick_detect_short_words(self, query: str) -> str | None:
        """Quick detection for short inputs using word dictionary. Returns None if not detected."""
        words = query.lower().strip().split()
        if len(words) > 3:
            return None

        # Check each word against dictionaries
        de_matches = sum(1 for w in words if w in SHORT_WORDS_DE)
        en_matches = sum(1 for w in words if w in SHORT_WORDS_EN)

        if de_matches > en_matches:
            logger.info(f"Quick detection: '{query}' -> German (dictionary match)")
            return 'de'
        elif en_matches > de_matches:
            logger.info(f"Quick detection: '{query}' -> English (dictionary match)")
            return 'en'

        return None

    def detect_language(self, query: str) -> str:
        # Try quick detection for short inputs first
        quick_result = self._quick_detect_short_words(query)
        if quick_result:
            return quick_result

        # Fall back to LLM for longer/ambiguous inputs
        prompt = promptconf.get_language_detector_prompt(query)
        messages = [HumanMessage(prompt)]

        try:
            result = self._model.invoke(messages)
            return result.language_code
        except Exception as e:
            logger.error(f"Failed to detect language: {e}")
            return ""