// Package deploy copies items from a discovery.Tree onto the filesystem,
// preserving executable bits and writing atomically (temp + rename).
package deploy

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

	"github.com/m3tam3re/agent-lib/internal/discovery"
)

// Dir copies a folder item (e.g. one skill) from the tree into dst,
// replacing whatever occupied dst before.
func Dir(tree discovery.Tree, srcRel, dst string) error {
	lister, ok := tree.(interface {
		FilesUnder(prefix string) ([]string, error)
	})
	if !ok {
		return fmt.Errorf("tree does not support directory copy")
	}
	files, err := lister.FilesUnder(srcRel)
	if err != nil {
		return err
	}
	if len(files) == 0 {
		return fmt.Errorf("no files under %s", srcRel)
	}
	parent := filepath.Dir(dst)
	if err := os.MkdirAll(parent, 0o755); err != nil {
		return err
	}
	tmp, err := os.MkdirTemp(parent, ".agent-lib-tmp-")
	if err != nil {
		return err
	}
	defer os.RemoveAll(tmp)
	prefix := strings.TrimSuffix(srcRel, "/") + "/"
	for _, f := range files {
		relInside := strings.TrimPrefix(f, prefix)
		target := filepath.Join(tmp, filepath.FromSlash(relInside))
		if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
			return err
		}
		if err := File(tree, f, target); err != nil {
			return err
		}
	}
	if err := os.RemoveAll(dst); err != nil {
		return err
	}
	return os.Rename(tmp, dst)
}

// File copies a single file from the tree to dst via temp file + rename.
func File(tree discovery.Tree, srcRel, dst string) error {
	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		return err
	}
	if mt, ok := tree.(interface {
		MaterializeFile(rel, dst string) error
	}); ok {
		tmp := dst + ".agent-lib-tmp"
		if err := mt.MaterializeFile(srcRel, tmp); err != nil {
			return err
		}
		return os.Rename(tmp, dst)
	}
	data, err := tree.ReadFile(srcRel)
	if err != nil {
		return err
	}
	tmp := dst + ".agent-lib-tmp"
	if err := os.WriteFile(tmp, data, 0o644); err != nil {
		return err
	}
	return os.Rename(tmp, dst)
}