package service

import (
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

// Settings configures the Metis service runtime.
type Settings struct {
	BindAddr         string
	InventoryPath    string
	CacheDir         string
	ArtifactDir      string
	HistoryPath      string
	SnapshotsPath    string
	TargetsPath      string
	DefaultFlashHost string
	FlashHosts       []string
	LocalHost        string
	AllowedGroups    []string
	MaxDeviceBytes   int64
}

// FromEnv builds service settings with sensible defaults for local dev and in-cluster use.
func FromEnv() Settings {
	dataDir := getenvDefault("METIS_DATA_DIR", "/var/lib/metis")
	localHost := getenvDefault("METIS_LOCAL_HOST", hostnameOr("unknown"))
	defaultFlashHost := getenvDefault("METIS_DEFAULT_FLASH_HOST", localHost)
	flashHosts := splitList(getenvDefault("METIS_FLASH_HOSTS", defaultFlashHost))
	return Settings{
		BindAddr:         getenvDefault("METIS_BIND_ADDR", ":8080"),
		InventoryPath:    getenvDefault("METIS_INVENTORY_PATH", "inventory.titan-rpi4.yaml"),
		CacheDir:         getenvDefault("METIS_CACHE_DIR", filepath.Join(dataDir, "cache")),
		ArtifactDir:      getenvDefault("METIS_ARTIFACT_DIR", filepath.Join(dataDir, "artifacts")),
		HistoryPath:      getenvDefault("METIS_HISTORY_PATH", filepath.Join(dataDir, "history.jsonl")),
		SnapshotsPath:    getenvDefault("METIS_SNAPSHOTS_PATH", filepath.Join(dataDir, "snapshots.json")),
		TargetsPath:      getenvDefault("METIS_TARGETS_PATH", filepath.Join(dataDir, "targets.json")),
		DefaultFlashHost: defaultFlashHost,
		FlashHosts:       flashHosts,
		LocalHost:        localHost,
		AllowedGroups:    splitList(getenvDefault("METIS_ALLOWED_GROUPS", "admin,maintainer")),
		MaxDeviceBytes:   getenvInt64("METIS_MAX_DEVICE_BYTES", 300000000000),
	}
}

func getenvDefault(key, fallback string) string {
	if value := strings.TrimSpace(os.Getenv(key)); value != "" {
		return value
	}
	return fallback
}

func getenvInt64(key string, fallback int64) int64 {
	raw := strings.TrimSpace(os.Getenv(key))
	if raw == "" {
		return fallback
	}
	value, err := strconv.ParseInt(raw, 10, 64)
	if err != nil {
		return fallback
	}
	return value
}

func splitList(raw string) []string {
	if strings.TrimSpace(raw) == "" {
		return nil
	}
	parts := strings.Split(raw, ",")
	result := make([]string, 0, len(parts))
	for _, part := range parts {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		result = append(result, part)
	}
	return result
}

func hostnameOr(fallback string) string {
	name, err := os.Hostname()
	if err != nil || strings.TrimSpace(name) == "" {
		return fallback
	}
	return strings.TrimSpace(name)
}