// Copyright 2022 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package pull

import (
	"context"
	"slices"

	"code.gitea.io/gitea/models/db"
	issues_model "code.gitea.io/gitea/models/issues"
	user_model "code.gitea.io/gitea/models/user"
	"code.gitea.io/gitea/modules/container"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/gitrepo"
	"code.gitea.io/gitea/modules/json"
	"code.gitea.io/gitea/modules/log"
)

const maxPushCommitsInCommentCount = 1000

func preparePushPullCommentPushActionContent(ctx context.Context, pr *issues_model.PullRequest, oldCommitID, newCommitID string, isForcePush bool) (data issues_model.PushActionContent, shouldCreate bool, err error) {
	if isForcePush {
		// if it's a force push, we need to get the whole pull request commits
		// the force-push timeline comment should always be created, so all errors are ignored and logged only.
		mergeBase, err := gitrepo.MergeBase(ctx, pr.BaseRepo, pr.BaseBranch, newCommitID)
		if err != nil {
			log.Debug("MergeBase %q..%q failed: %v", pr.BaseBranch, newCommitID, err)
		} else {
			data.CommitIDs, err = gitrepo.GetCommitIDsBetweenReverse(ctx, pr.BaseRepo, mergeBase, newCommitID, "", maxPushCommitsInCommentCount)
			if err != nil {
				log.Debug("GetCommitIDsBetweenReverse %q..%q failed: %v", mergeBase, newCommitID, err)
			}
		}
		return data, true, nil
	}

	// for a normal push, it maybe an empty pull request, only non-empty pull request need to create push comment
	data.CommitIDs, err = gitrepo.GetCommitIDsBetweenReverse(ctx, pr.BaseRepo, oldCommitID, newCommitID, pr.BaseBranch, maxPushCommitsInCommentCount)
	return data, len(data.CommitIDs) > 0, err
}

func reconcileOldCommitCommentsForForcePush(ctx context.Context, oldCommitComments []*issues_model.Comment, newData *issues_model.PushActionContent) (needDeleteCommentIDs []int64) {
	newPushCommitIDMaps := container.SetOf(newData.CommitIDs...)
	for _, oldCommitComment := range oldCommitComments {
		oldData, err := oldCommitComment.GetPushActionContent()
		if err != nil {
			continue
		}
		if oldData.IsForcePush {
			// old comment is for force push, it should be kept
			continue
		}

		// remove the old comment's commit IDs which are not in the new "force" push
		oldData.CommitIDs = slices.DeleteFunc(oldData.CommitIDs, func(oldCommitID string) bool { return !newPushCommitIDMaps.Contains(oldCommitID) })
		// if old comment doesn't contain any commit ID after the force push, then it can be deleted
		if len(oldData.CommitIDs) == 0 {
			needDeleteCommentIDs = append(needDeleteCommentIDs, oldCommitComment.ID)
			continue
		}
		// remove new comment's commit IDs which are already in old comment
		for _, oldCommitID := range oldData.CommitIDs {
			newData.CommitIDs = slices.DeleteFunc(newData.CommitIDs, func(newCommitID string) bool { return newCommitID == oldCommitID })
		}

		// update the old comment's content (the commit IDs have been changed)
		updatedOldContent, _ := json.Marshal(oldData)
		_, err = db.GetEngine(ctx).ID(oldCommitComment.ID).Cols("content").NoAutoTime().Update(&issues_model.Comment{Content: string(updatedOldContent)})
		if err != nil {
			log.Error("Update Comment content failed: %v", err)
		}
	}
	return needDeleteCommentIDs
}

func cleanUpOldCommitCommentsForNewForcePush(ctx context.Context, pr *issues_model.PullRequest, data *issues_model.PushActionContent) error {
	// All old non-force-push commit comments will be deleted if they are not in the new commit list.
	var oldCommitComments []*issues_model.Comment
	err := db.GetEngine(ctx).Table("comment").
		Where("issue_id = ?", pr.IssueID).And("type = ?", issues_model.CommentTypePullRequestPush).
		Find(&oldCommitComments)
	if err != nil {
		return err
	}

	needDeleteCommentIDs := reconcileOldCommitCommentsForForcePush(ctx, oldCommitComments, data)
	if len(needDeleteCommentIDs) == 0 {
		return nil
	}
	_, err = db.GetEngine(ctx).In("id", needDeleteCommentIDs).Delete(&issues_model.Comment{})
	return err
}

// CreatePushPullComment create push code to pull base comment
func CreatePushPullComment(ctx context.Context, pusher *user_model.User, pr *issues_model.PullRequest, oldRef, newRef string, isForcePush bool) (comment *issues_model.Comment, created bool, err error) {
	if pr.HasMerged || oldRef == "" || newRef == "" {
		return nil, false, nil
	}

	gitRepo, closer, err := gitrepo.RepositoryFromContextOrOpen(ctx, pr.BaseRepo)
	if err != nil {
		return nil, false, err
	}
	defer closer.Close()

	oldCommitID := oldRef
	if !git.IsEmptyCommitID(oldRef) {
		oldCommitID, err = gitRepo.GetRefCommitID(oldRef)
		if err != nil {
			return nil, false, err
		}
	}
	newCommitID, err := gitRepo.GetRefCommitID(newRef)
	if err != nil {
		return nil, false, err
	}

	data, shouldCreate, err := preparePushPullCommentPushActionContent(ctx, pr, oldCommitID, newCommitID, isForcePush)
	if !shouldCreate {
		return nil, false, err
	}

	comment, err = db.WithTx2(ctx, func(ctx context.Context) (comment *issues_model.Comment, err error) {
		if isForcePush {
			err := cleanUpOldCommitCommentsForNewForcePush(ctx, pr, &data)
			if err != nil {
				log.Error("CleanUpOldCommitComments failed: %v", err)
			}
		}

		if len(data.CommitIDs) > 0 {
			// if the push has commit IDs, add a "normal push" commit comment
			dataJSON, _ := json.Marshal(data)
			opts := &issues_model.CreateCommentOptions{
				Type:    issues_model.CommentTypePullRequestPush,
				Doer:    pusher,
				Repo:    pr.BaseRepo,
				Issue:   pr.Issue,
				Content: string(dataJSON),
			}
			comment, err = issues_model.CreateComment(ctx, opts)
			if err != nil {
				return nil, err
			}
		}

		if isForcePush {
			// if it's a force push, we need to add a force push comment
			forcePushDataJSON, _ := json.Marshal(&issues_model.PushActionContent{IsForcePush: true, CommitIDs: []string{oldCommitID, newCommitID}})
			opts := &issues_model.CreateCommentOptions{
				Type:    issues_model.CommentTypePullRequestPush,
				Doer:    pusher,
				Repo:    pr.BaseRepo,
				Issue:   pr.Issue,
				Content: string(forcePushDataJSON),

				// It seems the field is unnecessary anymore because PushActionContent includes IsForcePush field.
				// However, it can't be simply removed.
				IsForcePush: true, // See the comment of "Comment.IsForcePush"
			}
			comment, err = issues_model.CreateComment(ctx, opts)
			if err != nil {
				return nil, err
			}
		}
		return comment, nil
	})
	return comment, comment != nil, err
}