// Package config resolves where ipswap keeps its files and loads the settings
// that are not presets.
package config

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

// AppName is the single place the product name appears. It decides the data
// directory, the log file name and the tray tooltip prefix, so renaming the app
// is a one-line change here.
const AppName = "ipswap"

// Paths are the absolute locations of everything ipswap reads or writes.
type Paths struct {
	Dir     string
	Presets string
	Config  string
	Log     string
}

// ResolvePaths returns the data locations under %APPDATA%\ipswap on Windows.
//
// os.UserConfigDir maps to %APPDATA% on Windows and to ~/.config elsewhere,
// which keeps development on Linux from scribbling in odd places.
func ResolvePaths() (Paths, error) {
	base, err := os.UserConfigDir()
	if err != nil {
		return Paths{}, fmt.Errorf("locating the application data directory: %w", err)
	}
	dir := filepath.Join(base, AppName)
	return Paths{
		Dir:     dir,
		Presets: filepath.Join(dir, "presets.json"),
		Config:  filepath.Join(dir, "config.json"),
		Log:     filepath.Join(dir, AppName+".log"),
	}, nil
}

// MaskStyle is how subnet masks are displayed in the editor. Input always
// accepts both spellings; this only controls what is rendered back.
type MaskStyle string

const (
	MaskPrefix MaskStyle = "prefix" // /24
	MaskDotted MaskStyle = "dotted" // 255.255.255.0
)

// Settings is config.json.
type Settings struct {
	// MaskStyle is global rather than per-preset: a per-preset display
	// preference would be more state than the feature is worth.
	MaskStyle MaskStyle `json:"mask_style"`

	// StartWithWindows drives the HKCU Run key. Assumed default off; see the
	// open questions at the bottom of claude.md.
	StartWithWindows bool `json:"start_with_windows"`

	// CheckUpdates gates the startup call to the Gitea releases API.
	CheckUpdates bool `json:"check_updates"`

	// UpdateRepo is the Gitea repo polled for releases, as
	// "https://host/owner/repo". Empty disables the update checker entirely,
	// which is what a fork or a private build should set it to.
	UpdateRepo string `json:"update_repo"`

	// ActivePollSeconds is how often the live adapter state is re-read to work
	// out which preset is currently applied.
	ActivePollSeconds int `json:"active_poll_seconds"`
}

// Default is the settings a fresh install starts with.
// DefaultUpdateRepo is where release builds look for updates. Set it to "" in
// config.json (or clear the field in Settings) to turn the check off entirely.
const DefaultUpdateRepo = "https://gitea.apointless.space/bsncubed/ipswap"

func Default() Settings {
	return Settings{
		MaskStyle:         MaskPrefix,
		StartWithWindows:  false,
		CheckUpdates:      true,
		UpdateRepo:        DefaultUpdateRepo,
		ActivePollSeconds: 30,
	}
}

// DottedMasks reports whether masks should render as dotted quads.
func (s Settings) DottedMasks() bool { return s.MaskStyle == MaskDotted }

// Load reads config.json, falling back to defaults for a missing file or any
// field left unset. Settings are conveniences, so a corrupt config should not
// stop the app from starting — the caller logs the error and carries on.
func Load(path string) (Settings, error) {
	s := Default()

	b, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return s, nil
	}
	if err != nil {
		return s, fmt.Errorf("reading %s: %w", path, err)
	}

	if err := json.Unmarshal(b, &s); err != nil {
		return Default(), fmt.Errorf("parsing %s: %w", path, err)
	}

	// Repair anything nonsensical rather than refusing to run.
	if s.MaskStyle != MaskPrefix && s.MaskStyle != MaskDotted {
		s.MaskStyle = MaskPrefix
	}
	if s.ActivePollSeconds < 5 {
		s.ActivePollSeconds = 30
	}
	return s, nil
}

// Save writes config.json.
func (s Settings) Save(path string) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("creating config directory: %w", err)
	}
	b, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return fmt.Errorf("encoding settings: %w", err)
	}
	if err := os.WriteFile(path, append(b, '\n'), 0o644); err != nil {
		return fmt.Errorf("writing %s: %w", path, err)
	}
	return nil
}