"""Application settings with composition pattern."""

from enum import Enum
from functools import cached_property

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


class Environment(str, Enum):
    """Application environment modes."""

    DEV = "dev"
    PROD = "prod"


class AppConfig(BaseSettings):
    """Application configuration."""

    name: str = "Blog API"
    debug: bool = False
    host: str = "0.0.0.0"
    port: int = 8000

    model_config = SettingsConfigDict(
        env_prefix="APP_",
        env_file_encoding="utf-8",
        case_sensitive=False,
    )


class DBConfig(BaseSettings):
    """Database configuration."""

    # For dev: sqlite+aiosqlite:///./blog.db
    # For prod: postgresql+asyncpg://user:pass@host:port/db
    url: str | None = None
    echo: bool = False

    # PostgreSQL-specific settings (used in prod)
    host: str = "localhost"
    port: int = 5432
    user: str = "postgres"
    password: str = "postgres"
    name: str = "blog"

    model_config = SettingsConfigDict(
        env_prefix="DB_",
        env_file_encoding="utf-8",
        case_sensitive=False,
    )

    @field_validator("url")
    @classmethod
    def validate_url(cls, v: str | None) -> str | None:
        """Validate database URL if provided."""
        if v is None:
            return v
        if not any(v.startswith(prefix) for prefix in ("sqlite+", "postgresql+")):
            raise ValueError("Database URL must start with 'sqlite+' or 'postgresql+'")
        return v


class KCConfig(BaseSettings):
    """Keycloak configuration."""

    server_url: str = "http://localhost:8080"
    realm: str = "blog"
    client_id: str = "blog-api"
    client_secret: str = Field(
        default="",
        description="Keycloak client secret - must be set via env in production",
    )
    token_cache_ttl: int = 60  # seconds

    model_config = SettingsConfigDict(
        env_prefix="KC_",
        env_file_encoding="utf-8",
        case_sensitive=False,
    )

    @property
    def is_configured(self) -> bool:
        """Check if Keycloak is properly configured."""
        return bool(self.client_secret)


class SecurityConfig(BaseSettings):
    """Security configuration."""

    secret_key: str = Field(
        default="", description="Secret key for JWT - must be set via env in production"
    )
    access_token_expire_minutes: int = 30

    model_config = SettingsConfigDict(
        env_prefix="SECURITY_",
        env_file_encoding="utf-8",
        case_sensitive=False,
    )

    @property
    def is_configured(self) -> bool:
        """Check if security is properly configured."""
        return bool(self.secret_key)


class Settings(BaseSettings):
    """Application configuration settings with composition."""

    # Environment mode
    environment: Environment = Environment.DEV

    # Sub-configurations
    app: AppConfig = Field(default_factory=AppConfig)
    db: DBConfig = Field(default_factory=DBConfig)
    kc: KCConfig = Field(default_factory=KCConfig)
    security: SecurityConfig = Field(default_factory=SecurityConfig)

    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False,
        env_nested_delimiter="__",
    )

    def model_post_init(self, __context: object) -> None:
        """Validate settings after initialization."""
        if self.is_prod:
            if not self.security.is_configured:
                raise ValueError("SECURITY_SECRET_KEY must be set in production mode")
            if not self.kc.is_configured:
                raise ValueError("KC_CLIENT_SECRET must be set in production mode")

    @cached_property
    def database_url(self) -> str:
        """Get database URL based on environment.

        - In dev: uses SQLite if no URL provided
        - In prod: uses PostgreSQL if no URL provided
        """
        if self.db.url:
            return self.db.url

        if self.environment == Environment.PROD:
            # Build PostgreSQL URL from components
            return str(
                PostgresDsn.build(
                    scheme="postgresql+asyncpg",
                    username=self.db.user,
                    password=self.db.password,
                    host=self.db.host,
                    port=self.db.port,
                    path=self.db.name,
                )
            )

        # Default dev SQLite URL
        return "sqlite+aiosqlite:///./blog.db"

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

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


# Global settings instance
settings = Settings()