package gitcmd

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

func commandFailure(operation string, err error, stdout, stderr string) error {
	return fmt.Errorf("%s: %w\nstdout:\n%s\nstderr:\n%s",
		operation, err, strings.TrimSpace(stdout), strings.TrimSpace(stderr))
}

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, stderr, err := NewCommand("diff", "--name-only", "--diff-filter=U").WithDir(dir).RunStdString(r.ctx)
	if err != nil {
		return nil, commandFailure("list unmerged paths", err, out, stderr)
	}
	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()
	identityEnv := []string{
		"GIT_AUTHOR_NAME=" + authorName,
		"GIT_AUTHOR_EMAIL=" + authorEmail,
		"GIT_COMMITTER_NAME=" + authorName,
		"GIT_COMMITTER_EMAIL=" + authorEmail,
	}

	if !noFF && r.isAncestor(baseSHA, headSHA) {
		stdout, stderr, err := NewCommand("merge", "--ff-only").AddDynamicArguments(headSHA).
			WithDir(temp).WithEnv(identityEnv...).RunStdString(r.ctx)
		if err != nil {
			return nil, commandFailure("merge --ff-only", err, stdout, stderr)
		}
		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
	}

	mergeOut, mergeErrOut, mergeErr := NewCommand("merge", "--no-ff", "--no-commit").
		AddDynamicArguments(headSHA).WithDir(temp).WithEnv(identityEnv...).RunStdString(r.ctx)
	if mergeErr != nil {
		conflicts, err := r.unmergedPaths(temp)
		if err != nil {
			return nil, fmt.Errorf("%w\nmerge stdout:\n%s\nmerge stderr:\n%s",
				err, strings.TrimSpace(mergeOut), strings.TrimSpace(mergeErrOut))
		}
		if len(conflicts) == 0 {
			return nil, commandFailure("merge --no-ff --no-commit", mergeErr, mergeOut, mergeErrOut)
		}
		abortOut, abortErrOut, abortErr := NewCommand("merge", "--abort").WithDir(temp).RunStdString(r.ctx)
		if abortErr != nil {
			return nil, commandFailure("merge --abort", abortErr, abortOut, abortErrOut)
		}
		return &MergeResult{Base: base, Head: head, Conflicts: conflicts}, nil
	}

	treeOut, treeErrOut, err := NewCommand("write-tree").WithDir(temp).RunStdString(r.ctx)
	if err != nil {
		return nil, commandFailure("write-tree", err, treeOut, treeErrOut)
	}
	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
}