"""
Configuration management for AI Skills API.
Supports YAML config file with environment variable overrides.
"""

import os
from dataclasses import dataclass, field
from typing import List
import yaml


@dataclass
class RAGConfig:
    max_skills: int = 3
    max_conventions: int = 2
    max_snippets: int = 2
    min_skill_score: float = 0.3
    min_snippet_score: float = 0.25
    embedding_model: str = "all-MiniLM-L6-v2"


@dataclass
class CompressionConfig:
    enabled: bool = True
    strategy: str = "extractive"
    keep_last_n: int = 3
    max_tokens: int = 2000
    ollama_model: str = "phi3:mini"
    ollama_url: str = "http://localhost:11434"


@dataclass
class AuthConfig:
    enabled: bool = False
    api_key: str = "change-me-in-production"
    header_name: str = "X-API-Key"


@dataclass
class LoggingConfig:
    level: str = "INFO"
    format: str = "json"


@dataclass
class Config:
    host: str = "0.0.0.0"
    port: int = 8675
    database_url: str = "sqlite+aiosqlite:///./ai.db"
    rag: RAGConfig = field(default_factory=RAGConfig)
    compression: CompressionConfig = field(default_factory=CompressionConfig)
    auth: AuthConfig = field(default_factory=AuthConfig)
    logging: LoggingConfig = field(default_factory=LoggingConfig)
    cors_origins: List[str] = field(default_factory=lambda: ["*"])


def _coerce_value(value, cast_type):
    """Coerce string to type"""
    if cast_type is bool:
        return str(value).lower() in ('true', '1', 'yes', 'on')
    if cast_type is int:
        return int(value)
    if cast_type is float:
        return float(value)
    if cast_type is list:
        return str(value).split(',') if value else []
    return str(value) if value is not None else None


def load_config(config_path: str = "/app/config.yaml") -> Config:
    """Load configuration from YAML file with environment overrides"""
    # Find config file
    locations = [config_path, "/app/config.yaml", "./config.yaml"]
    file_data = {}
    
    for path in locations:
        if os.path.exists(path):
            with open(path, 'r') as f:
                file_data = yaml.safe_load(f) or {}
            break
    
    # Helper to get value: env > file > default
    def get(prefix, key, default, cast=None):
        env_key = f"{prefix}_{key}".upper() if prefix else key.upper()
        env_val = os.getenv(env_key)
        if env_val is not None:
            return _coerce_value(env_val, cast if cast else type(default))
        if key in file_data:
            return file_data[key]
        return default
    
    # Build nested configs
    rag_file = file_data.get('rag', {})
    rag = RAGConfig(
        max_skills=get('RAG', 'MAX_SKILLS', rag_file.get('max_skills', 3), int),
        max_conventions=get('RAG', 'MAX_CONVENTIONS', rag_file.get('max_conventions', 2), int),
        max_snippets=get('RAG', 'MAX_SNIPPETS', rag_file.get('max_snippets', 2), int),
        min_skill_score=get('RAG', 'MIN_SKILL_SCORE', rag_file.get('min_skill_score', 0.3), float),
        min_snippet_score=get('RAG', 'MIN_SNIPPET_SCORE', rag_file.get('min_snippet_score', 0.25), float),
        embedding_model=get('RAG', 'EMBEDDING_MODEL', rag_file.get('embedding_model', 'all-MiniLM-L6-v2'), str),
    )
    
    comp_file = file_data.get('compression', {})
    compression = CompressionConfig(
        enabled=get('COMPRESSION', 'ENABLED', comp_file.get('enabled', True), bool),
        strategy=get('COMPRESSION', 'STRATEGY', comp_file.get('strategy', 'extractive'), str),
        keep_last_n=get('COMPRESSION', 'KEEP_LAST_N', comp_file.get('keep_last_n', 3), int),
        max_tokens=get('COMPRESSION', 'MAX_TOKENS', comp_file.get('max_tokens', 2000), int),
        ollama_model=get('COMPRESSION', 'OLLAMA_MODEL', comp_file.get('ollama_model', 'phi3:mini'), str),
        ollama_url=get('COMPRESSION', 'OLLAMA_URL', comp_file.get('ollama_url', 'http://localhost:11434'), str),
    )
    
    auth_file = file_data.get('auth', {})
    auth = AuthConfig(
        enabled=get('AUTH', 'ENABLED', auth_file.get('enabled', False), bool),
        api_key=os.getenv('API_KEY', auth_file.get('api_key', 'change-me-in-production')),
        header_name=get('AUTH', 'HEADER_NAME', auth_file.get('header_name', 'X-API-Key'), str),
    )
    
    log_file = file_data.get('logging', {})
    logging = LoggingConfig(
        level=get('LOGGING', 'LEVEL', log_file.get('level', 'INFO'), str),
        format=get('LOGGING', 'FORMAT', log_file.get('format', 'json'), str),
    )
    
    return Config(
        host=get('APP', 'HOST', file_data.get('host', '0.0.0.0'), str),
        port=get('APP', 'PORT', file_data.get('port', 8675), int),
        database_url=os.getenv('DATABASE_URL', file_data.get('database_url', 'sqlite+aiosqlite:///./ai.db')),
        rag=rag,
        compression=compression,
        auth=auth,
        logging=logging,
        cors_origins=file_data.get('cors_origins', ["*"])
    )