package git

import (
	"context"
	"fmt"
	"path"
	"strings"
)

type TaggedSource struct {
	Head          string
	Status        string
	TagObject     string
	TagCommit     string
	TagObjectType string
}

// InspectTaggedSource reads the local HEAD, worktree state, and selected tag.
// Both lightweight historical tags and annotated tags are supported.
func InspectTaggedSource(ctx context.Context, repositoryDir, version string) (TaggedSource, error) {
	if !validVersionRef(version) {
		return TaggedSource{}, fmt.Errorf("invalid tag version %q", version)
	}
	var source TaggedSource
	head, err := run(ctx, repositoryDir, nil, "rev-parse", "--verify", "HEAD^{commit}")
	if err != nil {
		return TaggedSource{}, fmt.Errorf("read checkout HEAD: %w", err)
	}
	source.Head = strings.TrimSpace(head)
	if !validObjectID(source.Head) {
		return TaggedSource{}, fmt.Errorf("Git returned an invalid checkout commit %q", source.Head)
	}
	status, err := run(ctx, repositoryDir, nil, "status", "--porcelain", "--untracked-files=all")
	if err != nil {
		return TaggedSource{}, fmt.Errorf("inspect tagged checkout state: %w", err)
	}
	source.Status = strings.TrimSpace(status)
	ref := "refs/tags/" + version
	object, err := run(ctx, repositoryDir, nil, "rev-parse", "--verify", ref)
	if err != nil {
		return TaggedSource{}, fmt.Errorf("read local tag %s: %w", version, err)
	}
	source.TagObject = strings.TrimSpace(object)
	if !validObjectID(source.TagObject) {
		return TaggedSource{}, fmt.Errorf("Git returned an invalid tag object %q", source.TagObject)
	}
	peeled, err := run(ctx, repositoryDir, nil, "rev-parse", "--verify", ref+"^{commit}")
	if err != nil {
		return TaggedSource{}, fmt.Errorf("resolve local tag %s to a commit: %w", version, err)
	}
	source.TagCommit = strings.TrimSpace(peeled)
	if !validObjectID(source.TagCommit) {
		return TaggedSource{}, fmt.Errorf("Git returned an invalid tagged commit %q", source.TagCommit)
	}
	tagType, err := run(ctx, repositoryDir, nil, "cat-file", "-t", ref)
	if err != nil {
		return TaggedSource{}, fmt.Errorf("inspect local tag %s: %w", version, err)
	}
	source.TagObjectType = strings.TrimSpace(tagType)
	if source.TagObjectType != "tag" && source.TagObjectType != "commit" {
		return TaggedSource{}, fmt.Errorf("local tag %s has unsupported object type %q", version, source.TagObjectType)
	}
	return source, nil
}

// ReadCommitFile reads a repository-relative file from a specific commit.
func ReadCommitFile(ctx context.Context, repositoryDir, commit, name string) ([]byte, error) {
	if !validObjectID(commit) || name == "" || path.IsAbs(name) || path.Clean(name) != name || strings.HasPrefix(name, "../") || name == ".." || strings.Contains(name, "\\") {
		return nil, fmt.Errorf("invalid committed file identity %q at %q", name, commit)
	}
	content, err := run(ctx, repositoryDir, nil, "show", commit+":"+name)
	if err != nil {
		return nil, fmt.Errorf("read committed file %q: %w", name, err)
	}
	return []byte(content), nil
}