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

import json
import os
from pathlib import Path
from typing import Any, List, Optional

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict

try:
    from dotenv import load_dotenv
except ImportError:  # pragma: no cover - optional dependency in some runtimes
    load_dotenv = None

def _prime_process_env_from_dotenv() -> None:
    """Load .env into process env early."""
    if load_dotenv is None:
        return

    cwd_env = Path.cwd() / ".env"
    engine_env = Path(__file__).resolve().parent.parent / ".env"
    load_dotenv(dotenv_path=cwd_env, override=False)
    if engine_env != cwd_env:
        load_dotenv(dotenv_path=engine_env, override=False)


_prime_process_env_from_dotenv()


class Settings(BaseSettings):
    """Application settings loaded from environment variables."""

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

    # Server Configuration
    host: str = Field(default="0.0.0.0", description="Server host address")
    port: int = Field(default=8000, description="Server port")
    external_ip: Optional[str] = Field(default=None, description="External IP for NAT traversal")

    # Audio Configuration
    sample_rate: int = Field(default=16000, description="Audio sample rate in Hz")
    chunk_size_ms: int = Field(default=20, description="Audio chunk duration in milliseconds")
    default_codec: str = Field(default="pcm", description="Default audio codec")
    max_audio_buffer_seconds: int = Field(
        default=30,
        description="Maximum buffered user audio duration kept in memory for current turn"
    )

    # VAD Configuration
    vad_type: str = Field(default="silero", description="VAD algorithm type")
    vad_model_path: str = Field(default="data/vad/silero_vad.onnx", description="Path to VAD model")
    vad_threshold: float = Field(default=0.5, description="VAD detection threshold")
    vad_min_speech_duration_ms: int = Field(default=100, description="Minimum speech duration in milliseconds")
    vad_eou_threshold_ms: int = Field(default=800, description="End of utterance (silence) threshold in milliseconds")

    # LLM Configuration
    llm_provider: str = Field(
        default="openai",
        description="LLM provider (openai, openai_compatible, siliconflow)"
    )
    llm_api_url: Optional[str] = Field(default=None, description="LLM provider API base URL")
    llm_model: str = Field(default="gpt-4o-mini", description="LLM model name")
    llm_temperature: float = Field(default=0.7, description="LLM temperature for response generation")
    
    # TTS Configuration
    tts_provider: str = Field(
        default="openai_compatible",
        description="TTS provider (openai_compatible, siliconflow, dashscope)"
    )
    tts_api_url: Optional[str] = Field(default=None, description="TTS provider API URL")
    tts_model: Optional[str] = Field(default=None, description="TTS model name")
    tts_voice: str = Field(default="anna", description="TTS voice name")
    tts_mode: str = Field(
        default="commit",
        description="DashScope-only TTS mode (commit, server_commit). Ignored for non-dashscope providers."
    )
    tts_speed: float = Field(default=1.0, description="TTS speech speed multiplier")
    
    # ASR Configuration
    asr_provider: str = Field(
        default="openai_compatible",
        description="ASR provider (openai_compatible, buffered, siliconflow, dashscope)"
    )
    asr_api_url: Optional[str] = Field(default=None, description="ASR provider API URL")
    asr_model: Optional[str] = Field(default=None, description="ASR model name")
    asr_interim_interval_ms: int = Field(default=500, description="Interval for interim ASR results in ms")
    asr_min_audio_ms: int = Field(default=300, description="Minimum audio duration before first ASR result")
    asr_start_min_speech_ms: int = Field(
        default=160,
        description="Minimum continuous speech duration before ASR capture starts"
    )
    asr_pre_speech_ms: int = Field(
        default=240,
        description="Audio context (ms) prepended before detected speech to avoid clipping first phoneme"
    )
    asr_final_tail_ms: int = Field(
        default=120,
        description="Silence tail (ms) appended before final ASR decode to protect utterance ending"
    )
    
    # Duplex Pipeline Configuration
    duplex_enabled: bool = Field(default=True, description="Enable duplex voice pipeline")
    duplex_greeting: Optional[str] = Field(default=None, description="Optional greeting message")
    duplex_system_prompt: Optional[str] = Field(
        default="You are a helpful, friendly voice assistant. Keep your responses concise and conversational.",
        description="System prompt for LLM"
    )
    duplex_opener_audio_file: Optional[str] = Field(
        default=None,
        description="Optional opener audio file path for standalone engine mode (.pcm or .wav)"
    )
    
    # Barge-in (interruption) Configuration
    barge_in_min_duration_ms: int = Field(
        default=200, 
        description="Minimum speech duration (ms) required to trigger barge-in. Lower=more sensitive."
    )
    barge_in_silence_tolerance_ms: int = Field(
        default=60,
        description="How much silence (ms) is tolerated during potential barge-in before reset"
    )

    # Optional tool declarations from agent YAML.
    # Supports OpenAI function schema style entries and/or shorthand string names.
    tools: List[Any] = Field(default_factory=list, description="Default tool definitions for runtime")

    # Logging
    log_level: str = Field(default="INFO", description="Logging level")
    log_format: str = Field(default="json", description="Log format (json or text)")

    # CORS
    cors_origins: str = Field(
        default='["http://localhost:3000", "http://localhost:8080"]',
        description="CORS allowed origins"
    )

    # ICE Servers (WebRTC)
    ice_servers: str = Field(
        default='[{"urls": "stun:stun.l.google.com:19302"}]',
        description="ICE servers configuration"
    )

    # WebSocket heartbeat and inactivity
    inactivity_timeout_sec: int = Field(default=60, description="Close connection after no message from client (seconds)")
    heartbeat_interval_sec: int = Field(default=50, description="Send heartBeat event to client every N seconds")
    ws_protocol_version: str = Field(default="v1", description="Public WS protocol version")
    ws_emit_config_resolved: bool = Field(
        default=False,
        description="Emit config.resolved after session.started (debug/internal use; disabled for public SaaS by default)",
    )

    # Backend bridge configuration (for call/transcript persistence)
    backend_mode: str = Field(
        default="auto",
        description="Backend integration mode: auto | http | disabled"
    )
    backend_url: Optional[str] = Field(default=None, description="Backend API base URL (e.g. http://localhost:8787)")
    backend_timeout_sec: int = Field(default=10, description="Backend API request timeout in seconds")
    assistant_local_config_dir: str = Field(
        default="engine/config/agents",
        description="Directory containing local assistant runtime YAML files"
    )
    history_enabled: bool = Field(default=True, description="Enable history write bridge")
    history_default_user_id: int = Field(default=1, description="Fallback user_id for history records")
    history_queue_max_size: int = Field(default=256, description="Max buffered transcript writes per session")
    history_retry_max_attempts: int = Field(default=2, description="Retry attempts for each transcript write")
    history_retry_backoff_sec: float = Field(default=0.2, description="Base retry backoff for transcript writes")
    history_finalize_drain_timeout_sec: float = Field(
        default=1.5,
        description="Max wait before finalizing history when queue is still draining"
    )

    @property
    def chunk_size_bytes(self) -> int:
        """Calculate chunk size in bytes based on sample rate and duration."""
        # 16-bit (2 bytes) per sample, mono channel
        return int(self.sample_rate * 2 * (self.chunk_size_ms / 1000.0))

    @property
    def cors_origins_list(self) -> List[str]:
        """Parse CORS origins from JSON string."""
        try:
            return json.loads(self.cors_origins)
        except json.JSONDecodeError:
            return ["http://localhost:3000", "http://localhost:8080"]

    @property
    def ice_servers_list(self) -> List[dict]:
        """Parse ICE servers from JSON string."""
        try:
            return json.loads(self.ice_servers)
        except json.JSONDecodeError:
            return [{"urls": "stun:stun.l.google.com:19302"}]


# Global settings instance
settings = Settings()


def get_settings() -> Settings:
    """Get application settings instance."""
    return settings