// Package config handles loading and validating configuration
// for the KAOS supervisor from environment variables.
package config

import (
	"bufio"
	"fmt"
	"os"
	"strings"
	"time"
)

// Config holds the supervisor configuration values.
type Config struct {
	// Timeout is the maximum duration for supervisor operations.
	Timeout time.Duration
	// ProjectPath is the root path of the project being supervised.
	ProjectPath string
	// TasksDir is the path to the TASKS directory.
	TasksDir string
	// Port is the HTTP server port.
	Port string
}

// Load reads configuration from environment variables.
// It first attempts to load a .env file from the current directory.
// Required variables: KAOS_TIMEOUT, KAOS_PROJECT_PATH.
func Load() (*Config, error) {
	loadEnvFile(".env")

	timeoutStr := os.Getenv("KAOS_TIMEOUT")
	if timeoutStr == "" {
		return nil, fmt.Errorf("KAOS_TIMEOUT environment variable is required")
	}

	timeout, err := time.ParseDuration(timeoutStr)
	if err != nil {
		return nil, fmt.Errorf("invalid KAOS_TIMEOUT value %q: %w", timeoutStr, err)
	}

	projectPath := os.Getenv("KAOS_PROJECT_PATH")
	if projectPath == "" {
		return nil, fmt.Errorf("KAOS_PROJECT_PATH environment variable is required")
	}

	tasksDir := os.Getenv("KAOS_TASKS_DIR")
	if tasksDir == "" {
		return nil, fmt.Errorf("KAOS_TASKS_DIR environment variable is required")
	}

	port := os.Getenv("KAOS_PORT")
	if port == "" {
		port = "8080"
	}

	return &Config{
		Timeout:     timeout,
		ProjectPath: projectPath,
		TasksDir:    tasksDir,
		Port:        port,
	}, nil
}

// loadEnvFile reads a .env file and sets environment variables
// that are not already set. Lines starting with # are ignored.
func loadEnvFile(path string) {
	f, err := os.Open(path)
	if err != nil {
		return
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		key, value, ok := strings.Cut(line, "=")
		if !ok {
			continue
		}

		key = strings.TrimSpace(key)
		value = strings.TrimSpace(value)

		// Don't override existing environment variables
		if _, exists := os.LookupEnv(key); !exists {
			os.Setenv(key, value)
		}
	}
}