package main

import (
	"fmt"
	"regexp"
	"runtime/debug"
	"slices"
	"strings"
	"sync"
	"time"

	"src.opensuse.org/autogits/common"
	"src.opensuse.org/autogits/common/gitea-generated/models"
)

type RepoInfo struct {
	Owner  string
	Name   string
	Branch string
}

type ReparentBot struct {
	configs  common.AutogitConfigs
	gitea    common.Gitea
	giteaUrl string

	botUser string

	maintainershipFetcher MaintainershipFetcher
}

func (bot *ReparentBot) ParseSourceReposFromIssue(issue *models.Issue) []RepoInfo {
	var sourceRepos []RepoInfo
	rx := regexp.MustCompile(`([_a-zA-Z0-9\.-]+)/([_a-zA-Z0-9\.-]+)(?:#([_a-zA-Z0-9\.\-/]+))?$`)

	for _, line := range strings.Split(issue.Body, "\n") {
		matches := rx.FindStringSubmatch(strings.TrimSpace(line))
		if len(matches) == 4 {
			sourceRepos = append(sourceRepos, RepoInfo{Owner: matches[1], Name: matches[2], Branch: matches[3]})
		}
	}
	return sourceRepos
}

type MaintainershipFetcher interface {
	FetchProjectMaintainershipData(gitea common.GiteaMaintainershipReader, config *common.AutogitConfig) (common.MaintainershipData, error)
}

type RealMaintainershipFetcher struct{}

func (f *RealMaintainershipFetcher) FetchProjectMaintainershipData(gitea common.GiteaMaintainershipReader, config *common.AutogitConfig) (common.MaintainershipData, error) {
	return common.FetchProjectMaintainershipData(gitea, config)
}

func (bot *ReparentBot) GetMaintainers(config *common.AutogitConfig) ([]string, error) {
	m, err := bot.maintainershipFetcher.FetchProjectMaintainershipData(bot.gitea, config)
	if err != nil {
		return nil, err
	}
	return m.ListProjectMaintainers(config.ReviewGroups), nil
}

var serializeMutex sync.Mutex

func (bot *ReparentBot) ProcessIssue(org, repo string, issue *models.Issue) error {
	defer func() {
		if r := recover(); r != nil {
			common.LogInfo("panic caught --- recovered")
			common.LogError(string(debug.Stack()))
		}
	}()

	serializeMutex.Lock()
	defer serializeMutex.Unlock()

	common.LogInfo(">>> Starting processing issue:", common.IssueToString(issue))
	defer common.LogInfo("<<< End processing issue:", common.IssueToString(issue))

	if issue.State == "closed" {
		return nil
	}

	if !strings.HasPrefix(strings.ToUpper(issue.Title), "[ADD]") {
		return nil
	}

	newRepoLabel := false
	for _, l := range issue.Labels {
		if l.Name == common.Label_NewRepository {
			newRepoLabel = true
			break
		}
	}

	if !newRepoLabel {
		common.LogDebug("Not a new repository. Nothing to do here.")
		return nil
	}

	bot.gitea.ResetTimelineCache(org, repo, issue.Index)
	timeline, err := bot.gitea.GetTimeline(org, repo, issue.Index)
	if err != nil {
		common.LogError("Failed to fetch issue timeline:", err)
		return err
	}

	sourceRepos := bot.ParseSourceReposFromIssue(issue)
	if len(sourceRepos) == 0 {
		common.LogDebug("Could not parse any source repos from issue body")
		return nil
	}

	targetBranch := strings.TrimPrefix(issue.Ref, "refs/heads/")

	config := bot.configs.GetPrjGitConfig(org, repo, targetBranch)
	if config == nil {
		for _, c := range bot.configs {
			if c.Organization == org && c.Branch == targetBranch {
				config = c
				break
			}
		}
	}
	if config == nil {
		return fmt.Errorf("no config found for %s/%s#%s", org, repo, targetBranch)
	}

	maintainers, err := bot.GetMaintainers(config)
	if err != nil {
		return err
	}

	if len(maintainers) == 0 {
		return fmt.Errorf("no maintainers found for %s/%s#%s", org, repo, targetBranch)
	}

	repos := make([]struct {
		repo *models.Repository
		name string
	}, len(sourceRepos))
	for idx, sourceInfo := range sourceRepos {
		source, err := bot.gitea.GetRepository(sourceInfo.Owner, sourceInfo.Name)
		branch := ""
		if sourceInfo.Branch != "" {
			branch = sourceInfo.Branch
		} else if source != nil {
			branch = source.DefaultBranch
		}
		repos[idx].name = sourceInfo.Owner + "/" + sourceInfo.Name + "#" + branch

		if err != nil {
			common.LogError("failed to fetch source repo", repos[idx].name, ":", err)
			return nil
		}
		if source == nil {
			msg := fmt.Sprintf("Source repository not found: %s", repos[idx].name)
			bot.AddCommentOnce(org, repo, issue.Index, timeline, msg)
			common.LogError(msg)
			return nil
		}

		if source.Parent != nil && source.Parent.Owner.UserName == config.Organization {
			common.LogDebug("Already reparented repo. Nothing to do here.")
			return nil
		}

		// README: issue creator *must be* owner of the repo, OR repository must not be a fork
		if issue.User == nil || issue.User.UserName != sourceInfo.Owner && source.Fork {
			user := "(nil)"
			if issue.User != nil {
				user = issue.User.UserName
			}
			msg := fmt.Sprintf("@%s: You are not the owner of %s and it is already a fork. Skipping.", user, repos[idx].name)
			bot.AddCommentOnce(org, repo, issue.Index, timeline, msg)
			return nil
		}

		// Check if already exists in target org
		existing, err := bot.gitea.GetRepository(org, sourceInfo.Name)
		if err == nil && existing != nil {
			bot.AddCommentOnce(org, repo, issue.Index, timeline, fmt.Sprintf("Repository %s already exists in organization.", sourceInfo.Name))
			return nil
		}

		repos[idx].repo = source
	}
	// Check for approval in comments
	approved := false
	for _, e := range timeline {
		if e.Type == common.TimelineCommentType_Comment &&
			e.User != nil &&
			bot.IsMaintainer(e.User.UserName, maintainers) &&
			bot.IsApproval(e.Body) &&
			e.Updated == e.Created {

			// Approval must be newer than the last issue update (with some tolerance for latency)
			// If the comment is significantly older than the issue update, it applies to an old version.
			// We use a 1-minute tolerance to avoid race conditions
			if time.Time(e.Created).Before(time.Time(issue.Updated).Add(-1*time.Minute)) && issue.Updated != issue.Created {
				common.LogDebug("Ignoring stale approval from %s (created: %v, issue updated: %v)", e.User.UserName, e.Created, issue.Updated)
				continue
			}

			approved = true
			break
		}
	}

	if approved {
		common.LogInfo("Issue approved, processing source repos...")
		if !common.IsDryRun {
			for _, source := range repos {
				r := source.repo
				_, err := bot.gitea.ReparentRepository(r.Owner.UserName, r.Name, org)
				if err != nil {
					common.LogError("Reparent failed for", source.name, ":", err)
					continue
				}
				bot.AddCommentOnce(org, repo, issue.Index, timeline, fmt.Sprintf("Repository %s forked successfully.", source.name))
			}
			// bot.gitea.UpdateIssue(org, repo, issue.Index, &models.EditIssueOption{State: "closed"})
		} else {
			common.LogInfo("Dry run: would process %d source repos for issue %d", len(sourceRepos), issue.Index)
		}
	} else {
		// Request review/assignment if not already done
		found := false
		for _, a := range issue.Assignees {
			if bot.IsMaintainer(a.UserName, maintainers) {
				found = true
				break
			}
		}

		if !found {
			common.LogInfo("Requesting review from maintainers:", maintainers)
			if !common.IsDryRun {
				_, err := bot.gitea.UpdateIssue(org, repo, issue.Index, &models.EditIssueOption{
					Assignees: maintainers,
				})
				if err != nil {
					common.LogError("Failed to assign maintainers:", err)
				}
				bot.AddCommentOnce(org, repo, issue.Index, timeline,
					"Review requested from maintainers: "+strings.Join(maintainers, ", "))
			}
		}
	}

	return nil
}

func (bot *ReparentBot) IsMaintainer(user string, maintainers []string) bool {
	return slices.Contains(maintainers, user)
}

func (bot *ReparentBot) IsApproval(body string) bool {
	body = strings.ToLower(strings.TrimSpace(body))
	return strings.Contains(body, "approved") || strings.Contains(body, "lgtm")
}

func (bot *ReparentBot) HasComment(timeline []*models.TimelineComment, message string) bool {
	for _, e := range timeline {
		if e.Type == common.TimelineCommentType_Comment && e.User != nil && e.User.UserName == bot.botUser && strings.TrimSpace(e.Body) == strings.TrimSpace(message) {
			return true
		}
	}
	return false
}

func (bot *ReparentBot) AddCommentOnce(org, repo string, index int64, timeline []*models.TimelineComment, msg string) {
	if bot.HasComment(timeline, msg) {
		return
	}
	bot.gitea.AddComment(&models.PullRequest{Base: &models.PRBranchInfo{Repo: &models.Repository{Owner: &models.User{UserName: org}, Name: repo}}, Index: index}, msg)
}