"""Configuration management using Pydantic settings."""

import os
from typing import List, Literal

from pydantic import Field, field_validator
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    """
    Application settings with environment variable support.

    Settings are loaded from (in order of precedence):
    1. Environment variables
    2. .env file (if present)
    3. Default values

    Works without .env file for HuggingFace Spaces and containerized deployments.
    """

    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False,
        extra="ignore",
        # Don't error if .env file is missing (for HF Spaces, Docker, etc.)
        env_ignore_empty=True,
    )

    # Application Settings
    app_name: str = Field(default="AI Writing Studio", description="Application name")
    app_version: str = Field(default="1.0.0", description="Application version")
    environment: Literal["development", "staging", "production"] = Field(
        default="development", description="Runtime environment"
    )
    debug: bool = Field(default=False, description="Enable debug mode")

    # Server Configuration
    host: str = Field(default="0.0.0.0", description="Server host")
    port: int = Field(default=7860, ge=1, le=65535, description="Server port")
    server_workers: int = Field(default=4, ge=1, description="Number of worker processes")

    # Model Configuration
    default_model: str = Field(
        default="google/flan-t5-base",
        description="Default HuggingFace model (instruction-tuned for revision)"
    )
    max_model_length: int = Field(default=512, ge=1, description="Maximum model input length")
    default_max_length: int = Field(default=512, ge=1, description="Default generation length")
    default_num_sequences: int = Field(default=1, ge=1, description="Number of sequences")

    # Security
    allowed_origins: str = Field(
        default="http://localhost:7860,http://127.0.0.1:7860",
        description="Comma-separated CORS origins",
    )
    rate_limit_per_minute: int = Field(default=10, ge=1, description="Rate limit per minute")
    max_text_length: int = Field(
        default=10000, ge=1, description="Maximum input text length"
    )
    enable_auth: bool = Field(default=False, description="Enable authentication")
    secret_key: str = Field(default="", description="Secret key for sessions")

    # Logging
    log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"] = Field(
        default="INFO", description="Logging level"
    )
    log_format: Literal["json", "text"] = Field(default="json", description="Log format")
    log_file_path: str = Field(default="./logs/app.log", description="Log file path")
    log_max_bytes: int = Field(default=10485760, ge=1, description="Max log file size")
    log_backup_count: int = Field(default=5, ge=0, description="Number of log backups")

    # Monitoring
    enable_metrics: bool = Field(default=True, description="Enable Prometheus metrics")
    metrics_port: int = Field(default=8000, ge=1, le=65535, description="Metrics port")

    # Cache Configuration
    enable_cache: bool = Field(default=True, description="Enable caching")
    cache_ttl: int = Field(default=3600, ge=1, description="Cache TTL in seconds")
    cache_max_size: int = Field(default=100, ge=1, description="Maximum cache entries")

    # Feature Flags
    enable_diff_highlighting: bool = Field(default=True, description="Enable diff view")
    enable_rubric_scoring: bool = Field(default=True, description="Enable rubric scoring")
    enable_prompt_packs: bool = Field(default=True, description="Enable prompt packs")

    @field_validator("allowed_origins")
    @classmethod
    def parse_origins(cls, v: str) -> List[str]:
        """Parse comma-separated origins into a list."""
        if isinstance(v, str):
            return [origin.strip() for origin in v.split(",") if origin.strip()]
        return v

    @field_validator("log_file_path")
    @classmethod
    def ensure_directory_exists(cls, v: str) -> str:
        """Ensure directory exists for file paths."""
        directory = os.path.dirname(v) if os.path.splitext(v)[1] else v
        if directory and not os.path.exists(directory):
            os.makedirs(directory, exist_ok=True)
        return v

    @property
    def is_production(self) -> bool:
        """Check if running in production."""
        return self.environment == "production"

    @property
    def is_development(self) -> bool:
        """Check if running in development."""
        return self.environment == "development"


# Global settings instance
settings = Settings()