package hooks

import (
	"embed"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
)

// templateFS is the checked-in git template directory. It ships real, copy-able
// hook scripts (one per git hook name) under template/hooks/. The daemon
// materializes it to <root>/template at startup and CreateRepo passes
// --template=<root>/template to `git init --bare`, so every new repo gets these
// hooks verbatim. This is the "template repo": a versioned, inspectable artifact
// rather than something generated from a Go string.
//
//go:embed template
var templateFS embed.FS

// TemplateDir returns the on-disk git template directory for root: <root>/template.
// CreateRepo passes --template=<TemplateDir> to `git init --bare`.
func TemplateDir(root string) string {
	return filepath.Join(root, "template")
}

// EnsureTemplate materializes the embedded template directory to <root>/template
// and returns the template dir. Files under hooks/ are made executable (go:embed
// does not preserve the executable bit). Idempotent: rewrites every file each
// call, so an updated template is picked up on the next daemon start.
func EnsureTemplate(root string) (string, error) {
	dst := TemplateDir(root)
	if err := os.MkdirAll(dst, 0o755); err != nil {
		return "", fmt.Errorf("hooks: mkdir template: %w", err)
	}
	err := fs.WalkDir(templateFS, "template", func(p string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			return os.MkdirAll(filepath.Join(root, p), 0o755)
		}
		data, err := templateFS.ReadFile(p)
		if err != nil {
			return fmt.Errorf("hooks: read embedded %s: %w", p, err)
		}
		out := filepath.Join(root, p)
		if err := os.WriteFile(out, data, 0o644); err != nil {
			return fmt.Errorf("hooks: write %s: %w", p, err)
		}
		// Hook scripts must be executable; go:embed does not preserve mode bits.
		if filepath.Dir(p) == "template/hooks" {
			if err := os.Chmod(out, 0o755); err != nil {
				return fmt.Errorf("hooks: chmod %s: %w", p, err)
			}
		}
		return nil
	})
	if err != nil {
		return "", err
	}
	return dst, nil
}