// Package config loads VibeSonic's process configuration from
// VIBESONIC_* environment variables. There is no config file: everything
// needed to run the server is available via the environment so the same
// binary works under systemd or Docker without a wrapper script.
package config

import (
	"fmt"
	"net/netip"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"
)

type Config struct {
	ListenAddr    string
	DataDir       string
	DBPath        string
	MusicDirs     []string
	FFmpegPath    string
	FFprobePath   string
	ScanInterval  time.Duration
	SessionSecret string
	CookieSecure  bool

	ExtAuth ExtAuthConfig
}

// ExtAuthConfig configures optional Navidrome-style externalized
// authentication: a trusted reverse proxy authenticates the browser user
// and passes their identity in a header. VibeSonic never talks to an
// identity provider itself.
type ExtAuthConfig struct {
	Enabled         bool
	TrustedSources  []netip.Prefix
	UserHeader      string
	LogoutURL       string
	AutoCreateUsers bool
}

// Load reads configuration from the environment, applying defaults for
// anything unset. It returns an error only for values that are set but
// invalid (e.g. an unparsable duration or CIDR).
func Load() (Config, error) {
	cfg := Config{
		ListenAddr:    envOr("VIBESONIC_LISTEN_ADDR", ":8080"),
		DataDir:       envOr("VIBESONIC_DATA_DIR", "/var/lib/vibesonic"),
		FFmpegPath:    envOr("VIBESONIC_FFMPEG_PATH", "ffmpeg"),
		FFprobePath:   envOr("VIBESONIC_FFPROBE_PATH", "ffprobe"),
		SessionSecret: os.Getenv("VIBESONIC_SESSION_SECRET"),
		CookieSecure:  envBool("VIBESONIC_COOKIE_SECURE", true),
	}
	cfg.DBPath = envOr("VIBESONIC_DB", filepath.Join(cfg.DataDir, "vibesonic.db"))

	if dirs := os.Getenv("VIBESONIC_MUSIC_DIRS"); dirs != "" {
		for _, d := range strings.Split(dirs, ":") {
			d = strings.TrimSpace(d)
			if d != "" {
				cfg.MusicDirs = append(cfg.MusicDirs, d)
			}
		}
	}

	interval := envOr("VIBESONIC_SCAN_INTERVAL", "1h")
	d, err := time.ParseDuration(interval)
	if err != nil {
		return cfg, fmt.Errorf("VIBESONIC_SCAN_INTERVAL: %w", err)
	}
	cfg.ScanInterval = d

	extauth, err := loadExtAuth()
	if err != nil {
		return cfg, err
	}
	cfg.ExtAuth = extauth

	return cfg, nil
}

func loadExtAuth() (ExtAuthConfig, error) {
	e := ExtAuthConfig{
		Enabled:         envBool("VIBESONIC_EXTAUTH_ENABLED", false),
		UserHeader:      envOr("VIBESONIC_EXTAUTH_USER_HEADER", "Remote-User"),
		LogoutURL:       os.Getenv("VIBESONIC_EXTAUTH_LOGOUT_URL"),
		AutoCreateUsers: envBool("VIBESONIC_EXTAUTH_AUTO_CREATE_USERS", true),
	}
	raw := os.Getenv("VIBESONIC_EXTAUTH_TRUSTED_SOURCES")
	if raw == "" {
		// No default trusted network: external auth must be explicitly
		// scoped to a real network before it can trust anything.
		return e, nil
	}
	for _, part := range strings.Split(raw, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		prefix, err := parseCIDROrIP(part)
		if err != nil {
			return e, fmt.Errorf("VIBESONIC_EXTAUTH_TRUSTED_SOURCES: %w", err)
		}
		e.TrustedSources = append(e.TrustedSources, prefix)
	}
	return e, nil
}

func parseCIDROrIP(s string) (netip.Prefix, error) {
	if p, err := netip.ParsePrefix(s); err == nil {
		return p, nil
	}
	addr, err := netip.ParseAddr(s)
	if err != nil {
		return netip.Prefix{}, fmt.Errorf("invalid CIDR or IP %q: %w", s, err)
	}
	return netip.PrefixFrom(addr, addr.BitLen()), nil
}

func envOr(key, def string) string {
	if v := os.Getenv(key); v != "" {
		return v
	}
	return def
}

func envBool(key string, def bool) bool {
	v := os.Getenv(key)
	if v == "" {
		return def
	}
	b, err := strconv.ParseBool(v)
	if err != nil {
		return def
	}
	return b
}