// Package theming applies a selected colorscheme across starship, zellij,
// yazi, lazygit, and NvChad. Themes are discovered from embedded manifest
// files under assets/<id>/theme.yaml at package init time.
package theming

import (
	"embed"
	"fmt"
	"io/fs"
	"path/filepath"
	"sort"

	"gopkg.in/yaml.v3"
)

//go:embed assets
var assetsFS embed.FS

// Theme describes a colorscheme discovered under assets/<id>/theme.yaml.
type Theme struct {
	ID          string
	DisplayName string
	NvChadTheme string
}

type manifest struct {
	DisplayName string `yaml:"display_name"`
	NvChad      string `yaml:"nvchad"`
}

var discovered []Theme

func init() {
	themes, err := discover()
	if err != nil {
		// Package is embed-only; discovery failure is a programmer error,
		// not runtime input. Panic so tests surface the mistake early.
		panic(fmt.Errorf("theming: discover themes: %w", err))
	}
	discovered = themes
}

func discover() ([]Theme, error) {
	entries, err := fs.ReadDir(assetsFS, "assets")
	if err != nil {
		return nil, err
	}
	var out []Theme
	for _, e := range entries {
		if !e.IsDir() {
			continue
		}
		id := e.Name()
		m, err := readManifest(id)
		if err != nil {
			return nil, fmt.Errorf("theme %q: %w", id, err)
		}
		out = append(out, Theme{ID: id, DisplayName: m.DisplayName, NvChadTheme: m.NvChad})
	}
	sort.Slice(out, func(i, j int) bool { return out[i].ID < out[j].ID })
	return out, nil
}

func readManifest(id string) (manifest, error) {
	data, err := assetsFS.ReadFile(filepath.Join("assets", id, "theme.yaml"))
	if err != nil {
		return manifest{}, err
	}
	var m manifest
	if err := yaml.Unmarshal(data, &m); err != nil {
		return manifest{}, err
	}
	if m.DisplayName == "" {
		return manifest{}, fmt.Errorf("empty display_name")
	}
	if m.NvChad == "" {
		return manifest{}, fmt.Errorf("empty nvchad")
	}
	return m, nil
}

// List returns the themes sorted by ID.
func List() []Theme {
	out := make([]Theme, len(discovered))
	copy(out, discovered)
	return out
}

// Get returns the theme with the given ID, if present.
func Get(id string) (Theme, bool) {
	for _, t := range discovered {
		if t.ID == id {
			return t, true
		}
	}
	return Theme{}, false
}