"""Configuration module for BtToxin Pipeline Web Backend.

Defines System Constraints and environment variable configuration.
Requirements: 7.5
"""

import os
from dataclasses import dataclass
from typing import List


@dataclass(frozen=True)
class SystemConstraints:
    """System constraints and limits for the BtToxin Pipeline Web application."""

    # Upload and storage limits
    MAX_UPLOAD_SIZE: int = 50 * 1024 * 1024  # 50 MB
    MIN_FREE_DISK_GB: int = 20  # Minimum free disk space in GB
    MAX_TOTAL_STORAGE_GB: int = 500  # Maximum total storage in GB

    # Task execution limits
    TASK_TIMEOUT: int = 6 * 60 * 60  # 6 hours in seconds (21600)
    TASK_THREADS: int = 4  # Default threads per task

    # Concurrency and queue limits
    WORKER_CONCURRENCY: int = 32  # Celery worker process concurrency
    MAX_ACTIVE_PIPELINES: int = 4  # Max concurrent Digger containers
    QUEUE_MAX_LENGTH: int = 1000  # Maximum queue length

    # Data retention
    RESULT_RETENTION_DAYS: int = 30  # Results kept for 30 days

    # Allowed file extensions
    ALLOWED_EXTENSIONS: tuple = (".fna", ".fa", ".fasta")

    # Valid nucleotide characters (uppercase and lowercase)
    VALID_NUCLEOTIDES: frozenset = frozenset("ATGCNatgcn")


class Settings:
    """Application settings loaded from environment variables."""

    def __init__(self):
        # Redis configuration
        self.redis_url: str = os.getenv("REDIS_URL", "redis://localhost:6379/0")

        # Jobs directory
        self.jobs_dir: str = os.getenv("JOBS_DIR", "/data/jobs")

        # Task execution settings (can override SystemConstraints defaults)
        self.task_timeout: int = int(
            os.getenv("TASK_TIMEOUT", str(SystemConstraints.TASK_TIMEOUT))
        )
        self.max_active_pipelines: int = int(
            os.getenv("MAX_ACTIVE_PIPELINES", str(SystemConstraints.MAX_ACTIVE_PIPELINES))
        )
        self.task_threads: int = int(
            os.getenv("TASK_THREADS", str(SystemConstraints.TASK_THREADS))
        )
        self.worker_concurrency: int = int(
            os.getenv("WORKER_CONCURRENCY", str(SystemConstraints.WORKER_CONCURRENCY))
        )

        # CORS settings
        self.cors_origins: List[str] = os.getenv(
            "CORS_ORIGINS", "*"
        ).split(",")

        # API settings
        self.api_prefix: str = "/api/v1"
        self.debug: bool = os.getenv("DEBUG", "false").lower() == "true"


# Global settings instance
settings = Settings()

# Global constraints instance
constraints = SystemConstraints()