// Package export writes the published tree to a directory, for static
// hosts and CI.
package export

import (
	"fmt"
	"os"
	"path/filepath"

	"git.pablomurad.com/pablo/patchwork/internal/render"
)

// Write puts every file of the tree under dir. It builds the new tree in a
// sibling directory and swaps it in, so a web server reading dir never sees
// a half-written export. Files in dir that Patchwork didn't write are lost:
// give Patchwork a directory of its own.
func Write(t *render.Tree, dir string) error {
	dir = filepath.Clean(dir)
	tmp := dir + ".tmp"
	old := dir + ".old"
	if err := os.RemoveAll(tmp); err != nil {
		return err
	}
	for _, p := range t.Paths() {
		dst := filepath.Join(tmp, filepath.FromSlash(p))
		if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
			return err
		}
		if err := os.WriteFile(dst, t.Files[p].Body, 0o644); err != nil {
			return err
		}
	}
	if err := os.RemoveAll(old); err != nil {
		return err
	}
	if _, err := os.Stat(dir); err == nil {
		if err := os.Rename(dir, old); err != nil {
			return fmt.Errorf("move old export aside: %w", err)
		}
	}
	if err := os.Rename(tmp, dir); err != nil {
		os.Rename(old, dir) // put the previous export back
		return fmt.Errorf("swap in new export: %w", err)
	}
	return os.RemoveAll(old)
}