// Package config persists the small amount of state a Jellyfin client needs
// between runs: the server URL, the access token and user id obtained at login,
// a stable per-install device id, and the last-used playback volume. It lives at
// ~/.config/tsplay/config.json (XDG_CONFIG_HOME honoured).
package config

import (
	"encoding/json"
	"os"
	"path/filepath"

	"github.com/google/uuid"
)

// Config is the on-disk state. Token/UserID are empty until a successful login;
// the TUI shows the login screen whenever Token is blank.
type Config struct {
	ServerURL string `json:"server_url"`
	Username  string `json:"username"`
	Token     string `json:"token"`
	UserID    string `json:"user_id"`
	DeviceID  string `json:"device_id"`
	// Volume is the last playback volume (mpv's 0-130 scale), remembered across
	// tracks and runs. A nil pointer means "never set" — distinct from 0, which
	// is a deliberate silent level.
	Volume *float64 `json:"volume,omitempty"`
}

// VolumeOr returns the saved volume, or def if none has been stored yet.
func (c *Config) VolumeOr(def float64) float64 {
	if c.Volume == nil {
		return def
	}
	return *c.Volume
}

// SetVolume records v as the remembered volume.
func (c *Config) SetVolume(v float64) {
	c.Volume = &v
}

// dir returns ~/.config/tsplay, creating it on demand.
func dir() (string, error) {
	base, err := os.UserConfigDir()
	if err != nil {
		return "", err
	}
	d := filepath.Join(base, "tsplay")
	if err := os.MkdirAll(d, 0o700); err != nil {
		return "", err
	}
	return d, nil
}

func path() (string, error) {
	d, err := dir()
	if err != nil {
		return "", err
	}
	return filepath.Join(d, "config.json"), nil
}

// Load reads the saved config. A missing file is not an error: it returns a
// fresh Config with a newly minted DeviceID so first-run login can proceed.
func Load() (*Config, error) {
	p, err := path()
	if err != nil {
		return nil, err
	}
	data, err := os.ReadFile(p)
	if os.IsNotExist(err) {
		return &Config{DeviceID: uuid.NewString()}, nil
	}
	if err != nil {
		return nil, err
	}
	var c Config
	if err := json.Unmarshal(data, &c); err != nil {
		return nil, err
	}
	if c.DeviceID == "" {
		c.DeviceID = uuid.NewString()
	}
	return &c, nil
}

// Save writes the config back to disk with 0600 perms (it holds a token).
func (c *Config) Save() error {
	p, err := path()
	if err != nil {
		return err
	}
	data, err := json.MarshalIndent(c, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(p, data, 0o600)
}

// LoggedIn reports whether we have credentials to talk to the server.
func (c *Config) LoggedIn() bool {
	return c.ServerURL != "" && c.Token != "" && c.UserID != ""
}