package gitcmd

import (
	"fmt"
	"os"
	"strings"
)

type FileCommitResult struct {
	Commit Commit `json:"commit"`
}

func (r *Repository) CreateOrUpdateFile(branch, path, content, message, authorName, authorEmail, expectedSHA string) (*FileCommitResult, error) {
	parent, err := r.refSHA("refs/heads/" + branch)
	if err != nil {
		return nil, err
	}
	if parent == "" && expectedSHA != "" {
		return nil, fmt.Errorf("branch %q does not exist but expectedSHA %s given", branch, expectedSHA)
	}
	if parent != "" && expectedSHA != "" && parent != expectedSHA {
		return nil, fmt.Errorf("branch %q moved: expected %s, current %s", branch, expectedSHA, parent)
	}

	blobSHA, err := r.hashObject(content, r.Path)
	if err != nil {
		return nil, err
	}

	newTree, err := r.withTempIndex(func(idx string) (string, error) {
		return r.buildTree(idx, parent, path, blobSHA, false)
	})
	if err != nil {
		return nil, err
	}

	var parents []string
	if parent != "" {
		parents = []string{parent}
	}
	commitSHA, err := r.commitTree(newTree, message, authorName, authorEmail, r.Path, parents...)
	if err != nil {
		return nil, err
	}
	if err := r.updateRef("refs/heads/"+branch, commitSHA, expectedSHA); err != nil {
		return nil, err
	}
	commit, err := r.GetCommit(commitSHA)
	if err != nil {
		return nil, err
	}
	return &FileCommitResult{Commit: *commit}, nil
}

func (r *Repository) DeleteFile(branch, path, message, authorName, authorEmail, expectedSHA string) (*FileCommitResult, error) {
	parent, err := r.refSHA("refs/heads/" + branch)
	if err != nil {
		return nil, err
	}
	if parent == "" {
		return nil, fmt.Errorf("branch %q is empty; nothing to delete", branch)
	}
	if expectedSHA != "" && parent != expectedSHA {
		return nil, fmt.Errorf("branch %q moved: expected %s, current %s", branch, expectedSHA, parent)
	}

	newTree, err := r.withTempIndex(func(idx string) (string, error) {
		return r.buildTree(idx, parent, path, "", true)
	})
	if err != nil {
		return nil, err
	}

	commitSHA, err := r.commitTree(newTree, message, authorName, authorEmail, r.Path, parent)
	if err != nil {
		return nil, err
	}
	if err := r.updateRef("refs/heads/"+branch, commitSHA, expectedSHA); err != nil {
		return nil, err
	}
	commit, err := r.GetCommit(commitSHA)
	if err != nil {
		return nil, err
	}
	return &FileCommitResult{Commit: *commit}, nil
}

func (r *Repository) withTempIndex(fn func(idx string) (string, error)) (string, error) {
	f, err := os.CreateTemp("", "simplegit-index-*")
	if err != nil {
		return "", err
	}
	name := f.Name()
	f.Close()

	_ = os.Remove(name)
	defer os.Remove(name)
	return fn(name)
}

func (r *Repository) buildTree(indexFile, parent, path, blobSHA string, remove bool) (string, error) {
	env := "GIT_INDEX_FILE=" + indexFile

	if parent != "" {
		if _, _, err := NewCommand("read-tree").
			AddDynamicArguments(parent).
			WithDir(r.Path).WithEnv(env).
			RunStdString(r.ctx); err != nil {
			return "", fmt.Errorf("read-tree: %w", err)
		}
	}

	if remove {
		if err := r.removePathFromIndex(r.Path, path, env); err != nil {
			return "", err
		}
	} else {

		if _, _, err := NewCommand("update-index", "--add", "--replace", "--cacheinfo").
			AddDynamicArguments("100644," + blobSHA + "," + path).
			WithDir(r.Path).WithEnv(env).
			RunStdString(r.ctx); err != nil {
			return "", fmt.Errorf("update-index --cacheinfo: %w", err)
		}
	}

	out, _, err := NewCommand("write-tree").
		WithDir(r.Path).WithEnv(env).
		RunStdString(r.ctx)
	if err != nil {
		return "", fmt.Errorf("write-tree: %w", err)
	}
	return strings.TrimSpace(out), nil
}