// Package config loads and saves the teleportfling settings file.
//
// The file is JSON at ~/.config/teleportfling/config.json and holds the
// user-visible knobs exposed by the GUI (name, port, quality, fps, source,
// audio, monitor). Secrets and runtime state are deliberately excluded.
package config

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

	"teleportfling/internal/flinger"
)

// Config mirrors flinger.Config with JSON tags for persistence.
type Config struct {
	Name        string  `json:"name"`
	Port        int     `json:"port"`
	Quality     int     `json:"quality"`
	FPS         int     `json:"fps"`
	Source      string  `json:"source"`
	Audio       bool    `json:"audio"`
	StreamIndex int     `json:"stream_index"`
	Scale       float64 `json:"scale"`
	// Announce is a *bool so an absent JSON key (older config files) keeps
	// the default instead of silently disabling announcements.
	Announce *bool `json:"announce"`
}

// Default returns the default configuration.
func Default() Config {
	c := flinger.DefaultConfig()
	announce := c.Announce
	return Config{
		Name:        c.Name,
		Port:        c.Port,
		Quality:     c.Quality,
		FPS:         c.FPS,
		Source:      c.Source,
		Audio:       c.Audio,
		StreamIndex: c.StreamIndex,
		Scale:       c.Scale,
		Announce:    &announce,
	}
}

// ToFlinger converts a persisted config to the engine config.
func (c Config) ToFlinger() flinger.Config {
	announce := true
	if c.Announce != nil {
		announce = *c.Announce
	}
	return flinger.Config{
		Name:        c.Name,
		Port:        c.Port,
		Quality:     c.Quality,
		FPS:         c.FPS,
		Source:      c.Source,
		Audio:       c.Audio,
		StreamIndex: c.StreamIndex,
		Scale:       c.Scale,
		Announce:    announce,
	}
}

// pathVar is the config file location; overridable in tests.
var pathVar = func() string {
	dir, err := os.UserConfigDir()
	if err != nil {
		dir = "."
	}
	return filepath.Join(dir, "teleportfling", "config.json")
}()

// Path returns the default config file location.
func Path() string {
	return pathVar
}

// Load reads the default config file, returning Default when it does not exist.
func Load() (Config, error) {
	return LoadFrom(Path())
}

// LoadFrom reads the config file at path, returning Default when it does not
// exist. This lets the CLI and GUI support custom --config paths.
func LoadFrom(path string) (Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return Default(), nil
		}
		return Config{}, err
	}

	var c Config
	if err := json.Unmarshal(data, &c); err != nil {
		return Config{}, err
	}

	// Fill any zero values with defaults so a hand-edited file still works.
	d := Default()
	if c.Port == 0 {
		c.Port = d.Port
	}
	if c.Quality == 0 {
		c.Quality = d.Quality
	}
	if c.FPS == 0 {
		c.FPS = d.FPS
	}
	if c.Source == "" {
		c.Source = d.Source
	}
	if c.Scale <= 0 || c.Scale > 1 {
		c.Scale = d.Scale
	}
	if c.Announce == nil {
		announce := true
		c.Announce = &announce
	}
	return c, nil
}

// Save writes the default config file, creating the directory if needed.
func Save(c Config) error {
	return SaveTo(Path(), c)
}

// SaveTo writes the config file at path, creating the directory if needed.
func SaveTo(path string, c Config) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return err
	}
	data, err := json.MarshalIndent(c, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(path, data, 0o600)
}