"""Telemetry client configuration."""

from __future__ import annotations

import os
import re
from dataclasses import dataclass, field

_HEX_64_RE = re.compile(r"^[0-9a-fA-F]{64}$")
_UUID_RE = re.compile(
    r"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$"
)


@dataclass
class TelemetryConfig:
    """Configuration for the telemetry client.

    Values can be provided directly or loaded from environment variables:
      - MOSAIC_TELEMETRY_ENABLED -> enabled
      - MOSAIC_TELEMETRY_SERVER_URL -> server_url
      - MOSAIC_TELEMETRY_API_KEY -> api_key
      - MOSAIC_TELEMETRY_INSTANCE_ID -> instance_id
    """

    server_url: str = ""
    api_key: str = ""
    instance_id: str = ""
    enabled: bool = True
    submit_interval_seconds: float = 300.0
    max_queue_size: int = 1000
    batch_size: int = 100
    request_timeout_seconds: float = 10.0
    prediction_cache_ttl_seconds: float = 21600.0
    dry_run: bool = False
    max_retries: int = 3
    user_agent: str = field(default="mosaicstack-telemetry-python/0.1.0")

    def __post_init__(self) -> None:
        """Load environment variable overrides and validate."""
        env_enabled = os.environ.get("MOSAIC_TELEMETRY_ENABLED")
        if env_enabled is not None:
            self.enabled = env_enabled.lower() in ("1", "true", "yes")

        env_url = os.environ.get("MOSAIC_TELEMETRY_SERVER_URL")
        if env_url and not self.server_url:
            self.server_url = env_url

        env_key = os.environ.get("MOSAIC_TELEMETRY_API_KEY")
        if env_key and not self.api_key:
            self.api_key = env_key

        env_instance = os.environ.get("MOSAIC_TELEMETRY_INSTANCE_ID")
        if env_instance and not self.instance_id:
            self.instance_id = env_instance

        # Strip trailing slashes from server_url
        self.server_url = self.server_url.rstrip("/")

    def validate(self) -> list[str]:
        """Validate configuration and return list of errors (empty if valid)."""
        errors: list[str] = []

        if not self.server_url:
            errors.append("server_url is required")
        elif not self.server_url.startswith(("http://", "https://")):
            errors.append("server_url must start with http:// or https://")

        if not self.api_key:
            errors.append("api_key is required")
        elif not _HEX_64_RE.match(self.api_key):
            errors.append("api_key must be a 64-character hex string")

        if not self.instance_id:
            errors.append("instance_id is required")
        elif not _UUID_RE.match(self.instance_id):
            errors.append("instance_id must be a valid UUID string")

        if self.submit_interval_seconds <= 0:
            errors.append("submit_interval_seconds must be positive")

        if self.max_queue_size <= 0:
            errors.append("max_queue_size must be positive")

        if self.batch_size <= 0 or self.batch_size > 100:
            errors.append("batch_size must be between 1 and 100")

        if self.request_timeout_seconds <= 0:
            errors.append("request_timeout_seconds must be positive")

        return errors