package content

import (
	"io/fs"
	"path"
	"sort"
	"strings"
)

// ExtrasDir is the directory inside a bundle holding supporting files — drafts, notes, logs, scans.
//
// A fixed name for now. The parked settings cascade would let a comic call it `process/` and a story `notes/`,
// which is a section-level setting and nothing reads one yet (`ideas/deferred-decisions.md`).
const ExtrasDir = "extras"

// Entry is one file or directory inside a bundle's extras.
type Entry struct {
	// Name is the entry's own name; Path is its path within the extras directory, which is what a URL carries.
	Name, Path string
	// Kind classifies the entry for a theme: markdown, text, image, pdf, audio, video, other, or dir.
	Kind string
	// Size is the file's length in bytes, zero for a directory.
	Size int64
	// IsDir is true for a directory, which a theme renders as something to open rather than to show.
	IsDir bool
}

// Extras lists everything inside a bundle's extras directory, depth first, sorted by path.
//
// Sorted so the sparse numeric-prefix convention orders a set without putting numbers in URLs (ADR-0016), and
// because a directory read has no order worth relying on. A bundle with no extras returns nothing, which is not
// an error — most bundles have none.
func Extras(fsys fs.FS, b Bundle) []Entry {
	assets, hasAssets := b.Assets()
	if !hasAssets || fsys == nil {
		return nil
	}
	root := path.Join(assets, ExtrasDir)
	var found []Entry
	err := fs.WalkDir(fsys, root, func(p string, d fs.DirEntry, err error) error {
		if err != nil || p == root {
			// A missing extras directory is the common case, not a problem to report.
			return nil
		}
		rel := strings.TrimPrefix(p, root+"/")
		entry := Entry{Name: d.Name(), Path: rel, IsDir: d.IsDir(), Kind: "dir"}
		if !d.IsDir() {
			entry.Kind = KindOf(d.Name())
			if info, statErr := d.Info(); statErr == nil {
				entry.Size = info.Size()
			}
		}
		found = append(found, entry)
		return nil
	})
	if err != nil {
		return nil
	}
	sort.Slice(found, func(i, j int) bool { return found[i].Path < found[j].Path })
	return found
}

// KindOf classifies a filename for a theme, by extension.
//
// By extension and not by content: reading every file to sniff it would turn listing a directory into reading
// it, and the answer only decides how a theme presents the entry.
func KindOf(name string) string {
	switch strings.ToLower(path.Ext(name)) {
	case ".md", ".markdown":
		return "markdown"
	case ".txt", ".log", ".csv", ".json", ".yaml", ".yml", ".toml":
		return "text"
	case ".jpg", ".jpeg", ".png", ".gif", ".webp", ".svg", ".avif":
		return "image"
	case ".pdf":
		return "pdf"
	case ".mp3", ".ogg", ".wav", ".flac", ".m4a":
		return "audio"
	case ".mp4", ".webm", ".mov":
		return "video"
	}
	return "other"
}

// ExtrasURL is the address of a bundle's extras listing, or of one entry within it.
func ExtrasURL(route, lang, entry string) string {
	base := URL(route, lang) + ExtrasDir + "/"
	if entry == "" {
		return base
	}
	return base + entry
}