"""
Configuration loader and validator for search engine configurations.

This module handles loading, parsing, and validating YAML configuration files
that define how search engine data should be indexed and searched.
"""

import yaml
import os
from typing import Dict, Any, List, Optional
from dataclasses import dataclass, field
from pathlib import Path

from .field_types import (
    FieldConfig, FieldType, AnalyzerType,
    FIELD_TYPE_MAP, ANALYZER_MAP
)


@dataclass
class IndexConfig:
    """Configuration for an index domain (e.g., default, title, brand)."""
    name: str
    label: str
    fields: List[str]  # List of field names to include
    analyzer: AnalyzerType
    boost: float = 1.0
    example: Optional[str] = None

    # Multi-language field mapping: {"zh": ["name"], "en": ["enSpuName"], "ru": ["ruSkuName"]}
    language_field_mapping: Optional[Dict[str, List[str]]] = None


@dataclass
class RankingConfig:
    """Configuration for ranking expressions."""
    expression: str  # e.g., "bm25() + 0.2*text_embedding_relevance()"
    description: str


@dataclass
class QueryConfig:
    """Configuration for query processing."""
    supported_languages: List[str] = field(default_factory=lambda: ["zh", "en"])
    default_language: str = "zh"
    enable_translation: bool = True
    enable_text_embedding: bool = True
    enable_query_rewrite: bool = True
    rewrite_dictionary: Dict[str, str] = field(default_factory=dict)

    # Translation API settings
    translation_api_key: Optional[str] = None
    translation_service: str = "deepl"  # deepl, google, etc.
    translation_glossary_id: Optional[str] = None  # DeepL glossary ID for custom terminology
    translation_context: str = "e-commerce product search"  # Context hint for translation

    # ES source fields configuration - fields to return in search results
    source_fields: List[str] = field(default_factory=lambda: [
        "id", "spuId", "skuNo", "spuNo", "title", "enSpuName", "brandId",
        "brandName", "enBrandName", "categoryId", "categoryName", "enCategoryName",
        "price", "originalPrice", "currency", "image", "status", "createdAt", "updatedAt"
    ])


@dataclass
class SPUConfig:
    """Configuration for SPU aggregation."""
    enabled: bool = False
    spu_field: Optional[str] = None  # Field containing SPU ID
    inner_hits_size: int = 3


@dataclass
class FunctionScoreConfig:
    """Function Score配置（ES层打分规则）"""
    score_mode: str = "sum"  # multiply, sum, avg, first, max, min
    boost_mode: str = "multiply"  # multiply, replace, sum, avg, max, min
    functions: List[Dict[str, Any]] = field(default_factory=list)


@dataclass
class RerankConfig:
    """本地重排配置（当前禁用）"""
    enabled: bool = False
    expression: str = ""
    description: str = ""


@dataclass
class SearchConfig:
    """Complete configuration for search engine (multi-tenant)."""
    # Field definitions
    fields: List[FieldConfig]

    # Index structure (query domains)
    indexes: List[IndexConfig]

    # Query processing
    query_config: QueryConfig

    # Ranking configuration
    ranking: RankingConfig

    # Function Score configuration (ES层打分)
    function_score: FunctionScoreConfig

    # Rerank configuration (本地重排)
    rerank: RerankConfig

    # SPU configuration
    spu_config: SPUConfig

    # ES index settings
    es_index_name: str
    es_settings: Dict[str, Any] = field(default_factory=dict)


class ConfigurationError(Exception):
    """Raised when configuration validation fails."""
    pass


class ConfigLoader:
    """Loads and validates unified search engine configuration from YAML file."""

    def __init__(self, config_file: str = "config/config.yaml"):
        self.config_file = Path(config_file)
    
    def _load_rewrite_dictionary(self) -> Dict[str, str]:
        """
        Load query rewrite dictionary from external file.
        
        Returns:
            Dictionary mapping query terms to rewritten queries
        """
        # Try config/query_rewrite.dict first
        dict_file = self.config_file.parent / "query_rewrite.dict"
        
        if not dict_file.exists():
            # Dictionary file is optional, return empty dict if not found
            return {}
        
        rewrite_dict = {}
        try:
            with open(dict_file, 'r', encoding='utf-8') as f:
                for line_num, line in enumerate(f, 1):
                    line = line.strip()
                    # Skip empty lines and comments
                    if not line or line.startswith('#'):
                        continue
                    
                    # Parse tab-separated format
                    parts = line.split('\t')
                    if len(parts) != 2:
                        print(f"Warning: Invalid format in {dict_file} line {line_num}: {line}")
                        continue
                    
                    key, value = parts
                    rewrite_dict[key.strip()] = value.strip()
        except Exception as e:
            print(f"Error loading rewrite dictionary from {dict_file}: {e}")
            return {}
        
        return rewrite_dict

    def load_config(self) -> SearchConfig:
        """
        Load unified configuration from YAML file.

        Returns:
            SearchConfig object

        Raises:
            ConfigurationError: If config file not found or invalid
        """
        if not self.config_file.exists():
            raise ConfigurationError(f"Configuration file not found: {self.config_file}")

        try:
            with open(self.config_file, 'r', encoding='utf-8') as f:
                config_data = yaml.safe_load(f)
        except yaml.YAMLError as e:
            raise ConfigurationError(f"Invalid YAML in {self.config_file}: {e}")

        return self._parse_config(config_data)

    def _parse_config(self, config_data: Dict[str, Any]) -> SearchConfig:
        """Parse configuration dictionary into SearchConfig object."""

        # Parse fields
        fields = []
        for field_data in config_data.get("fields", []):
            fields.append(self._parse_field_config(field_data))

        # Parse indexes
        indexes = []
        for index_data in config_data.get("indexes", []):
            indexes.append(self._parse_index_config(index_data))

        # Parse query config
        query_config_data = config_data.get("query_config", {})
        
        # Load rewrite dictionary from external file instead of config
        rewrite_dictionary = self._load_rewrite_dictionary()
        
        query_config = QueryConfig(
            supported_languages=query_config_data.get("supported_languages", ["zh", "en"]),
            default_language=query_config_data.get("default_language", "zh"),
            enable_translation=query_config_data.get("enable_translation", True),
            enable_text_embedding=query_config_data.get("enable_text_embedding", True),
            enable_query_rewrite=query_config_data.get("enable_query_rewrite", True),
            rewrite_dictionary=rewrite_dictionary,
            translation_api_key=query_config_data.get("translation_api_key"),
            translation_service=query_config_data.get("translation_service", "deepl"),
            translation_glossary_id=query_config_data.get("translation_glossary_id"),
            translation_context=query_config_data.get("translation_context", "e-commerce product search")
        )

        # Parse ranking config
        ranking_data = config_data.get("ranking", {})
        ranking = RankingConfig(
            expression=ranking_data.get("expression", "bm25() + 0.2*text_embedding_relevance()"),
            description=ranking_data.get("description", "Default BM25 + text embedding ranking")
        )

        # Parse Function Score configuration
        fs_data = config_data.get("function_score", {})
        function_score = FunctionScoreConfig(
            score_mode=fs_data.get("score_mode", "sum"),
            boost_mode=fs_data.get("boost_mode", "multiply"),
            functions=fs_data.get("functions", [])
        )

        # Parse Rerank configuration
        rerank_data = config_data.get("rerank", {})
        rerank = RerankConfig(
            enabled=rerank_data.get("enabled", False),
            expression=rerank_data.get("expression", ""),
            description=rerank_data.get("description", "")
        )

        # Parse SPU config
        spu_data = config_data.get("spu_config", {})
        spu_config = SPUConfig(
            enabled=spu_data.get("enabled", False),
            spu_field=spu_data.get("spu_field"),
            inner_hits_size=spu_data.get("inner_hits_size", 3)
        )

        return SearchConfig(
            fields=fields,
            indexes=indexes,
            query_config=query_config,
            ranking=ranking,
            function_score=function_score,
            rerank=rerank,
            spu_config=spu_config,
            es_index_name=config_data.get("es_index_name", "search_products"),
            es_settings=config_data.get("es_settings", {})
        )

    def _parse_field_config(self, field_data: Dict[str, Any]) -> FieldConfig:
        """Parse field configuration from dictionary."""
        name = field_data["name"]
        field_type_str = field_data["type"]

        # Map field type string to enum
        if field_type_str not in FIELD_TYPE_MAP:
            raise ConfigurationError(f"Unknown field type: {field_type_str}")
        field_type = FIELD_TYPE_MAP[field_type_str]

        # Map analyzer string to enum (if provided)
        analyzer = None
        analyzer_str = field_data.get("analyzer")
        if analyzer_str and analyzer_str in ANALYZER_MAP:
            analyzer = ANALYZER_MAP[analyzer_str]

        search_analyzer = None
        search_analyzer_str = field_data.get("search_analyzer")
        if search_analyzer_str and search_analyzer_str in ANALYZER_MAP:
            search_analyzer = ANALYZER_MAP[search_analyzer_str]

        return FieldConfig(
            name=name,
            field_type=field_type,
            analyzer=analyzer,
            search_analyzer=search_analyzer,
            required=field_data.get("required", False),
            multi_language=field_data.get("multi_language", False),
            languages=field_data.get("languages"),
            boost=field_data.get("boost", 1.0),
            store=field_data.get("store", False),
            index=field_data.get("index", True),
            embedding_dims=field_data.get("embedding_dims", 1024),
            embedding_similarity=field_data.get("embedding_similarity", "dot_product"),
            nested=field_data.get("nested", False),
            nested_properties=field_data.get("nested_properties")
        )

    def _parse_index_config(self, index_data: Dict[str, Any]) -> IndexConfig:
        """Parse index configuration from dictionary."""
        analyzer_str = index_data.get("analyzer", "chinese_ecommerce")
        if analyzer_str not in ANALYZER_MAP:
            raise ConfigurationError(f"Unknown analyzer: {analyzer_str}")

        # Parse language field mapping if present
        language_field_mapping = index_data.get("language_field_mapping")

        return IndexConfig(
            name=index_data["name"],
            label=index_data.get("label", index_data["name"]),
            fields=index_data["fields"],
            analyzer=ANALYZER_MAP[analyzer_str],
            boost=index_data.get("boost", 1.0),
            example=index_data.get("example"),
            language_field_mapping=language_field_mapping
        )

    def validate_config(self, config: SearchConfig) -> List[str]:
        """
        Validate search configuration.

        Args:
            config: Search configuration to validate

        Returns:
            List of validation error messages (empty if valid)
        """
        errors = []

        # Validate field references in indexes
        field_names = {field.name for field in config.fields}
        field_map = {field.name: field for field in config.fields}
        
        for index in config.indexes:
            # Validate fields in index.fields
            for field_name in index.fields:
                if field_name not in field_names:
                    errors.append(f"Index '{index.name}' references unknown field '{field_name}'")
            
            # Validate language_field_mapping if present
            if index.language_field_mapping:
                for lang, field_list in index.language_field_mapping.items():
                    if not isinstance(field_list, list):
                        errors.append(f"Index '{index.name}': language_field_mapping['{lang}'] must be a list")
                        continue
                    
                    for field_name in field_list:
                        # Check if field exists
                        if field_name not in field_names:
                            errors.append(
                                f"Index '{index.name}': language_field_mapping['{lang}'] "
                                f"references unknown field '{field_name}'"
                            )
                        else:
                            # Check if field is TEXT type (multi-language fields should be text fields)
                            field = field_map[field_name]
                            if field.field_type != FieldType.TEXT:
                                errors.append(
                                    f"Index '{index.name}': language_field_mapping['{lang}'] "
                                    f"field '{field_name}' must be of type TEXT, got {field.field_type.value}"
                                )
                            
                            # Verify analyzer is appropriate for the language
                            # This is a soft check - we just warn if analyzer doesn't match language
                            if field.analyzer:
                                analyzer_name = field.analyzer.value.lower()
                                expected_analyzers = {
                                    'zh': ['chinese', 'index_ansj', 'query_ansj'],
                                    'en': ['english'],
                                    'ru': ['russian'],
                                    'ar': ['arabic'],
                                    'es': ['spanish'],
                                    'ja': ['japanese']
                                }
                                if lang in expected_analyzers:
                                    expected = expected_analyzers[lang]
                                    if not any(exp in analyzer_name for exp in expected):
                                        # Warning only, not an error
                                        print(
                                            f"Warning: Index '{index.name}': field '{field_name}' for language '{lang}' "
                                            f"uses analyzer '{analyzer_name}', which may not be optimal for '{lang}'"
                                        )

        # Validate SPU config
        if config.spu_config.enabled:
            if not config.spu_config.spu_field:
                errors.append("SPU aggregation enabled but no spu_field specified")
            elif config.spu_config.spu_field not in field_names:
                errors.append(f"SPU field '{config.spu_config.spu_field}' not found in fields")

        # Validate embedding fields have proper configuration
        for field in config.fields:
            if field.field_type in [FieldType.TEXT_EMBEDDING, FieldType.IMAGE_EMBEDDING]:
                if field.embedding_dims <= 0:
                    errors.append(f"Field '{field.name}': embedding_dims must be positive")
                if field.embedding_similarity not in ["dot_product", "cosine", "l2_norm"]:
                    errors.append(f"Field '{field.name}': invalid embedding_similarity")

        # Validate tenant_id field (required)
        tenant_id_field = None
        for field in config.fields:
            if field.name == "tenant_id":
                tenant_id_field = field
                break
        
        if not tenant_id_field:
            errors.append("Required field 'tenant_id' not found in fields")
        elif not tenant_id_field.required:
            errors.append("Field 'tenant_id' must be marked as required")

        return errors

    def save_config(self, config: SearchConfig, output_path: Optional[str] = None) -> None:
        """
        Save configuration to YAML file.
        
        Note: rewrite_dictionary is saved separately to query_rewrite.dict file

        Args:
            config: Configuration to save
            output_path: Optional output path (defaults to config/config.yaml)
        """
        if output_path is None:
            output_path = self.config_file
        else:
            output_path = Path(output_path)

        # Convert config back to dictionary format
        config_dict = {
            "es_index_name": config.es_index_name,
            "es_settings": config.es_settings,
            "fields": [self._field_to_dict(field) for field in config.fields],
            "indexes": [self._index_to_dict(index) for index in config.indexes],
            "query_config": {
                "supported_languages": config.query_config.supported_languages,
                "default_language": config.query_config.default_language,
                "enable_translation": config.query_config.enable_translation,
                "enable_text_embedding": config.query_config.enable_text_embedding,
                "enable_query_rewrite": config.query_config.enable_query_rewrite,
                # rewrite_dictionary is stored in separate file, not in config
                "translation_api_key": config.query_config.translation_api_key,
                "translation_service": config.query_config.translation_service,
            },
            "ranking": {
                "expression": config.ranking.expression,
                "description": config.ranking.description
            },
            "function_score": {
                "score_mode": config.function_score.score_mode,
                "boost_mode": config.function_score.boost_mode,
                "functions": config.function_score.functions
            },
            "rerank": {
                "enabled": config.rerank.enabled,
                "expression": config.rerank.expression,
                "description": config.rerank.description
            },
            "spu_config": {
                "enabled": config.spu_config.enabled,
                "spu_field": config.spu_config.spu_field,
                "inner_hits_size": config.spu_config.inner_hits_size
            }
        }

        output_path.parent.mkdir(parents=True, exist_ok=True)
        with open(output_path, 'w', encoding='utf-8') as f:
            yaml.dump(config_dict, f, default_flow_style=False, allow_unicode=True)
        
        # Save rewrite dictionary to separate file
        self._save_rewrite_dictionary(config.query_config.rewrite_dictionary)
    
    def _save_rewrite_dictionary(self, rewrite_dict: Dict[str, str]) -> None:
        """
        Save rewrite dictionary to external file.
        
        Args:
            rewrite_dict: Dictionary to save
        """
        dict_file = self.config_file.parent / "query_rewrite.dict"
        dict_file.parent.mkdir(parents=True, exist_ok=True)
        
        with open(dict_file, 'w', encoding='utf-8') as f:
            for key, value in rewrite_dict.items():
                f.write(f"{key}\t{value}\n")

    def _field_to_dict(self, field: FieldConfig) -> Dict[str, Any]:
        """Convert FieldConfig to dictionary."""
        result = {
            "name": field.name,
            "type": field.field_type.value,
            "required": field.required,
            "boost": field.boost,
            "store": field.store,
            "index": field.index,
        }

        if field.analyzer:
            result["analyzer"] = field.analyzer.value
        if field.search_analyzer:
            result["search_analyzer"] = field.search_analyzer.value
        if field.multi_language:
            result["multi_language"] = field.multi_language
            result["languages"] = field.languages
        if field.embedding_dims != 1024:
            result["embedding_dims"] = field.embedding_dims
        if field.embedding_similarity != "dot_product":
            result["embedding_similarity"] = field.embedding_similarity
        if field.nested:
            result["nested"] = field.nested
            result["nested_properties"] = field.nested_properties

        return result

    def _index_to_dict(self, index: IndexConfig) -> Dict[str, Any]:
        """Convert IndexConfig to dictionary."""
        result = {
            "name": index.name,
            "label": index.label,
            "fields": index.fields,
            "analyzer": index.analyzer.value,
            "boost": index.boost,
            "example": index.example
        }

        if index.language_field_mapping:
            result["language_field_mapping"] = index.language_field_mapping

        return result