package gitcmd

import (
	"errors"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

func (r *Repository) tempWorkingClone(branch string) (temp string, cleanup func(), err error) {
	dir, err := os.MkdirTemp("", "simplegit-temprepo-*")
	if err != nil {
		return "", nil, err
	}
	temp = filepath.Join(dir, "repo")
	cleanup = func() { _ = os.RemoveAll(dir) }
	cmd := NewCommand("clone", "--shared").AddOptionValues("-b", branch).AddDynamicArguments(r.Path, temp)
	if _, _, err := cmd.RunStdString(r.ctx); err != nil {
		cleanup()
		return "", nil, fmt.Errorf("temp clone: %w", err)
	}
	return temp, cleanup, nil
}

func (r *Repository) unmergedPaths(dir string) ([]string, error) {
	out, _, err := NewCommand("diff", "--name-only", "--diff-filter=U").WithDir(dir).RunStdString(r.ctx)
	if err != nil {
		return nil, err
	}
	var paths []string
	for _, l := range strings.Split(out, "\n") {
		if l = strings.TrimSpace(l); l != "" {
			paths = append(paths, l)
		}
	}
	return paths, nil
}

func (r *Repository) MergeViaTempRepo(base, head, message, authorName, authorEmail string, noFF bool) (*MergeResult, error) {
	baseSHA, err := r.refSHA("refs/heads/" + base)
	if err != nil || baseSHA == "" {
		return nil, fmt.Errorf("base branch %q not found", base)
	}
	headSHA, err := r.refSHA("refs/heads/" + head)
	if err != nil || headSHA == "" {
		return nil, fmt.Errorf("head branch %q not found", head)
	}

	temp, cleanup, err := r.tempWorkingClone(base)
	if err != nil {
		return nil, err
	}
	defer cleanup()

	if !noFF && r.isAncestor(baseSHA, headSHA) {
		if _, _, err := NewCommand("merge", "--ff-only").AddDynamicArguments(headSHA).WithDir(temp).RunStdString(r.ctx); err != nil {
			return nil, fmt.Errorf("merge --ff-only: %w", err)
		}
		if err := r.pushBack(temp, base, headSHA, baseSHA); err != nil {
			return nil, err
		}
		hc, err := r.GetCommit(headSHA)
		if err != nil {
			return nil, err
		}
		return &MergeResult{Base: base, Head: head, MergeCommit: hc, FastForward: true}, nil
	}

	_, _, mergeErr := NewCommand("merge", "--no-ff", "--no-commit").
		AddDynamicArguments(headSHA).WithDir(temp).RunStdString(r.ctx)
	if mergeErr != nil {

		var exitErr *exec.ExitError
		if !errors.As(mergeErr, &exitErr) {
			return nil, fmt.Errorf("merge: %w", mergeErr)
		}
		conflicts, _ := r.unmergedPaths(temp)
		_, _, _ = NewCommand("merge", "--abort").WithDir(temp).RunStdString(r.ctx)
		return &MergeResult{Base: base, Head: head, Conflicts: conflicts}, nil
	}

	treeOut, _, err := NewCommand("write-tree").WithDir(temp).RunStdString(r.ctx)
	if err != nil {
		return nil, fmt.Errorf("write-tree: %w", err)
	}
	mergedTree := strings.TrimSpace(treeOut)
	commitSHA, err := r.commitTree(mergedTree, message, authorName, authorEmail, temp, baseSHA, headSHA)
	if err != nil {
		return nil, err
	}
	if err := r.pushBack(temp, base, commitSHA, baseSHA); err != nil {
		return nil, err
	}
	mc, err := r.GetCommit(commitSHA)
	if err != nil {
		return nil, err
	}
	return &MergeResult{Base: base, Head: head, MergeCommit: mc}, nil
}