package bundle

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

func ValidateManifest(manifest Manifest) error {
	if manifest.SchemaVersion != SchemaVersion {
		return fmt.Errorf("schema_version must be %d", SchemaVersion)
	}
	if manifest.ID == "" {
		return fmt.Errorf("id is required")
	}
	if err := validateDigest(manifest.Digest); err != nil {
		return fmt.Errorf("digest: %w", err)
	}
	if manifest.Created.IsZero() {
		return fmt.Errorf("created is required")
	}
	if len(manifest.Files) == 0 {
		return fmt.Errorf("files is required")
	}
	seen := make(map[string]struct{}, len(manifest.Files))
	for index, file := range manifest.Files {
		if err := ValidateSourcePath(file.Path); err != nil {
			return fmt.Errorf("files[%d].path: %w", index, err)
		}
		if err := validateDigest(file.SHA256); err != nil {
			return fmt.Errorf("files[%d].sha256: %w", index, err)
		}
		if file.Size < 0 {
			return fmt.Errorf("files[%d].size must be non-negative", index)
		}
		if _, exists := seen[file.Path]; exists {
			return fmt.Errorf("files[%d].path duplicates %q", index, file.Path)
		}
		seen[file.Path] = struct{}{}
	}
	if actual := BundleDigest(manifest.Files); actual != manifest.Digest {
		return fmt.Errorf("digest mismatch: got %s want %s", actual, manifest.Digest)
	}
	return nil
}

func ValidateBundle(root string, manifest Manifest) error {
	if err := ValidateManifest(manifest); err != nil {
		return err
	}
	files := append([]ManifestFile(nil), manifest.Files...)
	for index, manifestFile := range files {
		fullPath := filepath.Join(root, filepath.FromSlash(manifestFile.Path))
		info, err := os.Lstat(fullPath)
		if err != nil {
			return fmt.Errorf("file %q stat: %w", manifestFile.Path, err)
		}
		if !info.Mode().IsRegular() {
			return fmt.Errorf("file %q must be a regular file", manifestFile.Path)
		}
		if info.Size() != manifestFile.Size {
			return fmt.Errorf("file %q size mismatch: got %d want %d", manifestFile.Path, info.Size(), manifestFile.Size)
		}
		data, err := os.ReadFile(fullPath)
		if err != nil {
			return fmt.Errorf("file %q read: %w", manifestFile.Path, err)
		}
		actualDigest := FileDigest(data)
		if actualDigest != manifestFile.SHA256 {
			return fmt.Errorf("file %q sha256 mismatch: got %s want %s", manifestFile.Path, actualDigest, manifestFile.SHA256)
		}
		files[index].SHA256 = actualDigest
		files[index].Size = int64(len(data))
	}
	if actualDigest := BundleDigest(files); actualDigest != manifest.Digest {
		return fmt.Errorf("digest mismatch: got %s want %s", actualDigest, manifest.Digest)
	}
	return nil
}