// Package scaffold holds the documents kettle writes into a project: the slash
// commands an operator invokes, the skills a model loads, and the runner
// subagent.
//
// They live inside the binary rather than beside it. A plugin shipped this prose
// once, on its own release cadence, and nothing on an operator's machine checked
// that the plugin they had installed described the binary they had installed —
// so a renamed flag could ship with documentation recommending the old one,
// which is the exact failure the generated block was invented to prevent, one
// hop further downstream. Prose that travels inside the binary cannot be a
// version behind it.
//
// This package depends on nothing but the standard library and holds no
// rendering logic: it hands out embedded files and says which of them carry a
// generated region. Splicing the command registry into that region is
// internal/cmd's, because the registry is.
package scaffold

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

//go:embed all:assets
var assets embed.FS

const assetRoot = "assets"

// Marker is the directory these files are written into, relative to the project
// root. It belongs to the agent harness, not to kettle: everything kettle owns
// is under `.kettle/`, and this is the one tree it writes that somebody else
// defines the shape of.
const Marker = ".claude"

// generated maps an output path to the command group whose flag table belongs
// in it. A file that is not in here carries no generated region and is shipped
// exactly as embedded.
//
// Explicit rather than derived from the directory name: the group ⇄ skill
// correspondence is a decision, and one that has not always held — `init` and
// `auth` are commands with no skill of their own, and `project` is a skill
// covering four commands. A test in internal/cmd asserts every group in the
// registry is named here exactly once, so adding a group fails loudly rather
// than silently shipping a skill nobody can find.
var generated = map[string]string{
	"skills/kettle-project/SKILL.md": "project",
	"skills/kettle-issue/SKILL.md":   "issue",
	"skills/kettle-sync/SKILL.md":    "sync",
	"skills/kettle-api/SKILL.md":     "api",
}

// File is one document, ready to be written under the output directory.
type File struct {
	// Path is relative to the output directory, always with forward slashes:
	// "commands/kettle/init.md", "skills/kettle-issue/SKILL.md".
	Path string
	// Body is the file as embedded — before any generated region is spliced in.
	Body string
	// Group is the command group whose flag table belongs in this file, or "".
	Group string
}

// Files is every document, sorted by path.
//
// Sorted, not in walk order, because the sort is the promise: two runs of the
// same binary produce the same list, so a receipt and a --check diff are
// comparable between machines.
func Files() []File {
	var out []File
	_ = fs.WalkDir(assets, assetRoot, func(p string, d fs.DirEntry, err error) error {
		if err != nil || d.IsDir() {
			return err
		}
		rel := strings.TrimPrefix(p, assetRoot+"/")
		body, err := assets.ReadFile(p)
		if err != nil {
			return err
		}
		out = append(out, File{Path: rel, Body: string(body), Group: generated[rel]})
		return nil
	})
	sort.Slice(out, func(i, j int) bool { return out[i].Path < out[j].Path })
	return out
}

// Groups lists every command group that has a file here, sorted.
func Groups() []string {
	out := make([]string, 0, len(generated))
	for _, g := range generated {
		out = append(out, g)
	}
	sort.Strings(out)
	return out
}

// PathFor is the output path carrying a group's flag table, or "".
func PathFor(group string) string {
	for p, g := range generated {
		if g == group {
			return p
		}
	}
	return ""
}

// Dirs lists the directories the output tree is made of, parents first, so a
// caller can create them in order.
func Dirs() []string {
	seen := map[string]bool{}
	var out []string
	for _, f := range Files() {
		for _, d := range parents(path.Dir(f.Path)) {
			if !seen[d] {
				seen[d] = true
				out = append(out, d)
			}
		}
	}
	sort.Strings(out)
	return out
}

func parents(dir string) []string {
	if dir == "." || dir == "" {
		return nil
	}
	return append(parents(path.Dir(dir)), dir)
}