package validation

import (
	"context"
	"fmt"

	"gitea.maximumdirect.net/eric/ReleaseKit/internal/git"
)

// CandidateTree is an inventory of one captured commit with blob contents
// loaded lazily by object ID.
type CandidateTree struct {
	repositoryDir string
	entries       []git.TreeEntry
	byPath        map[string]int
	blobs         map[string][]byte
}

// ReadCandidateTree enumerates the captured commit without reading from the
// worktree.
func ReadCandidateTree(ctx context.Context, repositoryDir, commit string) (*CandidateTree, error) {
	entries, err := git.ReadTree(ctx, repositoryDir, commit)
	if err != nil {
		return nil, err
	}
	tree := &CandidateTree{
		repositoryDir: repositoryDir,
		entries:       entries,
		byPath:        make(map[string]int, len(entries)),
		blobs:         make(map[string][]byte),
	}
	for index, entry := range entries {
		tree.byPath[entry.Path] = index
	}
	return tree, nil
}

// Entries returns the committed tree metadata in Git's tree order.
func (tree *CandidateTree) Entries() []git.TreeEntry {
	return append([]git.TreeEntry(nil), tree.entries...)
}

// ReadFile returns the committed blob bytes for path. Contents are cached by
// object ID for later reads from this tree.
func (tree *CandidateTree) ReadFile(ctx context.Context, path string) ([]byte, error) {
	index, ok := tree.byPath[path]
	if !ok {
		return nil, fmt.Errorf("committed path %q does not exist", path)
	}
	entry := tree.entries[index]
	if entry.Type != "blob" {
		return nil, fmt.Errorf("committed path %q is a %s entry, not a blob", path, entry.Type)
	}
	if contents, ok := tree.blobs[entry.ObjectID]; ok {
		return append([]byte(nil), contents...), nil
	}
	contents, err := git.ReadBlob(ctx, tree.repositoryDir, entry.ObjectID)
	if err != nil {
		return nil, fmt.Errorf("read committed path %q: %w", path, err)
	}
	tree.blobs[entry.ObjectID] = append([]byte(nil), contents...)
	return contents, nil
}

// Entry returns the committed metadata for path when present.
func (tree *CandidateTree) Entry(path string) (git.TreeEntry, bool) {
	index, ok := tree.byPath[path]
	if !ok {
		return git.TreeEntry{}, false
	}
	return tree.entries[index], true
}