package common

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"path"
	"slices"
	"strings"

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

type PRInfo struct {
	PR         *models.PullRequest
	Reviews    *PRReviews
	RemoteName string
}

type PRSet struct {
	PRs    []*PRInfo
	Config *AutogitConfig

	BotUser string
}

func (prinfo *PRInfo) PRComponents() (org string, repo string, idx int64) {
	org = prinfo.PR.Base.Repo.Owner.UserName
	repo = prinfo.PR.Base.Repo.Name
	idx = prinfo.PR.Index
	return
}

func readPRData(gitea GiteaPRFetcher, pr *models.PullRequest, currentSet []*PRInfo, config *AutogitConfig) ([]*PRInfo, error) {
	for _, p := range currentSet {
		if pr.Index == p.PR.Index && pr.Base.Repo.Name == p.PR.Base.Repo.Name && pr.Base.Repo.Owner.UserName == p.PR.Base.Repo.Owner.UserName {
			return nil, nil
		}
	}
	retSet := []*PRInfo{&PRInfo{PR: pr}}

	// only need to extact there on PrjGit PR
	org, repo, _ := config.GetPrjGit()
	if pr.Base.Repo.Name == repo && pr.Base.Repo.Owner.UserName == org {
		_, refPRs := ExtractDescriptionAndPRs(bufio.NewScanner(strings.NewReader(pr.Body)))
		for _, prdata := range refPRs {
			pr, err := gitea.GetPullRequest(prdata.Org, prdata.Repo, prdata.Num)
			if err != nil {
				return nil, err
			}
			data, err := readPRData(gitea, pr, slices.Concat(currentSet, retSet), config)
			if err != nil {
				return nil, err
			}
			retSet = slices.Concat(retSet, data)
		}
	}

	return retSet, nil
}

var Timeline_RefIssueNotFound error = errors.New("RefIssue not found on the timeline")

func LastPrjGitRefOnTimeline(gitea GiteaPRTimelineFetcher, org, repo string, num int64, prjGitOrg, prjGitRepo string) (*models.PullRequest, error) {
	timeline, err := gitea.GetTimeline(org, repo, num)
	if err != nil {
		LogError("Failed to fetch timeline for", org, repo, "#", num, err)
		return nil, err
	}

	for idx := len(timeline) - 1; idx >= 0; idx-- {
		item := timeline[idx]
		issue := item.RefIssue
		if item.Type == TimelineCommentType_PullRequestRef &&
			issue != nil &&
			issue.Repository != nil &&
			issue.Repository.Owner == prjGitOrg &&
			issue.Repository.Name == prjGitRepo {

			_, prs := ExtractDescriptionAndPRs(bufio.NewScanner(strings.NewReader(item.RefIssue.Body)))
			for _, pr := range prs {
				if pr.Org == org && pr.Repo == repo && pr.Num == num {
					LogDebug("Found PrjGit PR in Timeline:", issue.Index)

					// found prjgit PR in timeline. Return it
					return gitea.GetPullRequest(prjGitOrg, prjGitRepo, issue.Index)
				}
			}
		}
	}

	LogDebug("PrjGit RefIssue not found on timeline in", org, repo, num)
	return nil, Timeline_RefIssueNotFound
}

func FetchPRSet(user string, gitea GiteaPRTimelineFetcher, org, repo string, num int64, config *AutogitConfig) (*PRSet, error) {
	var pr *models.PullRequest
	var err error

	prjGitOrg, prjGitRepo, _ := config.GetPrjGit()
	if prjGitOrg == org && prjGitRepo == repo {
		if pr, err = gitea.GetPullRequest(org, repo, num); err != nil {
			return nil, err
		}
	} else {
		if pr, err = LastPrjGitRefOnTimeline(gitea, org, repo, num, prjGitOrg, prjGitRepo); err != nil && err != Timeline_RefIssueNotFound {
			return nil, err
		}

		if pr == nil {
			if pr, err = gitea.GetPullRequest(org, repo, num); err != nil {
				return nil, err
			}
		}
	}

	prs, err := readPRData(gitea, pr, nil, config)
	if err != nil {
		return nil, err
	}

	return &PRSet{
		PRs:     prs,
		Config:  config,
		BotUser: user,
	}, nil
}

func (rs *PRSet) Find(pr *models.PullRequest) (*PRInfo, bool) {
	for _, p := range rs.PRs {
		if p.PR.Base.RepoID == pr.Base.RepoID &&
			p.PR.Head.Sha == pr.Head.Sha &&
			p.PR.Base.Name == pr.Base.Name {
			return p, true
		}
	}

	return nil, false
}

func (rs *PRSet) AddPR(pr *models.PullRequest) *PRInfo {
	if pr, found := rs.Find(pr); found {
		return pr
	}

	prinfo := &PRInfo{
		PR: pr,
	}
	rs.PRs = append(rs.PRs, prinfo)
	return prinfo
}

func (rs *PRSet) IsPrjGitPR(pr *models.PullRequest) bool {
	org, repo, branch := rs.Config.GetPrjGit()
	return pr.Base.Name == branch && pr.Base.Repo.Name == repo && pr.Base.Repo.Owner.UserName == org
}

var PRSet_PrjGitMissing error = errors.New("No PrjGit PR found")
var PRSet_MultiplePrjGit error = errors.New("Multiple PrjGit PRs in one review set")

func (rs *PRSet) GetPrjGitPR() (*PRInfo, error) {
	var ret *PRInfo

	for _, prinfo := range rs.PRs {
		if rs.IsPrjGitPR(prinfo.PR) {
			if ret == nil {
				ret = prinfo
			} else {
				return nil, PRSet_MultiplePrjGit
			}
		}
	}

	if ret != nil {
		return ret, nil
	}

	return nil, PRSet_PrjGitMissing
}

func (rs *PRSet) NeedRecreatingPrjGit(currentBranchHash string) bool {
	pr, err := rs.GetPrjGitPR()
	if err != nil {
		return true
	}

	return pr.PR.Base.Sha == currentBranchHash
}

func (rs *PRSet) IsConsistent() bool {
	prjpr_info, err := rs.GetPrjGitPR()
	if err != nil {
		return false
	}
	prjpr := prjpr_info.PR

	_, prjpr_set := ExtractDescriptionAndPRs(bufio.NewScanner(strings.NewReader(prjpr.Body)))
	if len(prjpr_set) != len(rs.PRs)-1 { // 1 to many mapping
		LogDebug("Number of PR from links:", len(prjpr_set), "is not what's expected", len(rs.PRs)-1)
		return false
	}

next_rs:
	for _, prinfo := range rs.PRs {
		if prinfo.PR.State != "open" {
			return false
		}

		if prjpr == prinfo.PR {
			continue
		}

		for _, pr := range prjpr_set {
			if prinfo.PR.Base.Repo.Owner.UserName == pr.Org && prinfo.PR.Base.Repo.Name == pr.Repo && prinfo.PR.Index == pr.Num {
				continue next_rs
			}
		}
		return false
	}
	return true
}

func (rs *PRSet) AssignReviewers(gitea GiteaReviewFetcherAndRequester, maintainers MaintainershipData) error {
	configReviewers := ParseReviewers(rs.Config.Reviewers)

	for _, pr := range rs.PRs {
		reviewers := []string{}

		if rs.IsPrjGitPR(pr.PR) {
			reviewers = slices.Concat(configReviewers.Prj, configReviewers.PrjOptional)
			LogDebug("PrjGit submitter:", pr.PR.User.UserName)
			if len(rs.PRs) == 1 {
				reviewers = slices.Concat(reviewers, maintainers.ListProjectMaintainers())
			}
		} else {
			pkg := pr.PR.Base.Repo.Name
			reviewers = slices.Concat(configReviewers.Pkg, maintainers.ListProjectMaintainers(), maintainers.ListPackageMaintainers(pkg), configReviewers.PkgOptional)
		}

		slices.Sort(reviewers)
		reviewers = slices.Compact(reviewers)

		// submitters do not need to review their own work
		if idx := slices.Index(reviewers, pr.PR.User.UserName); idx != -1 {
			reviewers = slices.Delete(reviewers, idx, idx+1)
		}

		LogDebug("PR: ", pr.PR.Base.Repo.Name, pr.PR.Index)
		LogDebug("reviewers for PR:", reviewers)

		// remove reviewers that were already requested and are not stale
		reviews, err := FetchGiteaReviews(gitea, reviewers, pr.PR.Base.Repo.Owner.UserName, pr.PR.Base.Repo.Name, pr.PR.Index)
		if err != nil {
			LogError("Error fetching reviews:", err)
			return err
		}

		for idx := 0; idx < len(reviewers); {
			user := reviewers[idx]
			if reviews.HasPendingReviewBy(user) || reviews.IsReviewedBy(user) {
				reviewers = slices.Delete(reviewers, idx, idx+1)
				LogDebug("removing reviewer:", user)
			} else {
				idx++
			}
		}

		// get maintainers associated with the PR too
		if len(reviewers) > 0 {
			LogDebug("Requesting reviews from:", reviewers)
			if !IsDryRun {
				for _, r := range reviewers {
					if _, err := gitea.RequestReviews(pr.PR, r); err != nil {
						LogError("Cannot create reviews on", fmt.Sprintf("%s/%s!%d for [%s]", pr.PR.Base.Repo.Owner.UserName, pr.PR.Base.Repo.Name, pr.PR.Index, strings.Join(reviewers, ", ")), err)
					}
				}
			}
		}
	}
	return nil
}

func (rs *PRSet) RemoveClosedPRs() {
	rs.PRs = slices.DeleteFunc(rs.PRs, func(pr *PRInfo) bool {
		return pr.PR.State != "open"
	})
}

func (rs *PRSet) IsApproved(gitea GiteaPRChecker, maintainers MaintainershipData) bool {
	configReviewers := ParseReviewers(rs.Config.Reviewers)

	is_manually_reviewed_ok := false

	if need_manual_review := rs.Config.ManualMergeOnly || rs.Config.ManualMergeProject; need_manual_review {
		prjgit, err := rs.GetPrjGitPR()
		if err == nil && prjgit != nil {
			reviewers := slices.Concat(configReviewers.Prj, maintainers.ListProjectMaintainers())
			LogDebug("Fetching reviews for", prjgit.PR.Base.Repo.Owner.UserName, prjgit.PR.Base.Repo.Name, prjgit.PR.Index)
			r, err := FetchGiteaReviews(gitea, reviewers, prjgit.PR.Base.Repo.Owner.UserName, prjgit.PR.Base.Repo.Name, prjgit.PR.Index)
			if err != nil {
				LogError("Cannot fetch gita reaviews for PR:", err)
				return false
			}
			prjgit.Reviews = r
			if prjgit.Reviews.IsManualMergeOK() {
				is_manually_reviewed_ok = true
			}
		}

		if !is_manually_reviewed_ok && !rs.Config.ManualMergeProject {
			for _, pr := range rs.PRs {
				if rs.IsPrjGitPR(pr.PR) {
					continue
				}

				pkg := pr.PR.Base.Repo.Name
				reviewers := slices.Concat(configReviewers.Pkg, maintainers.ListPackageMaintainers(pkg))
				LogDebug("Fetching reviews for", pr.PR.Base.Repo.Owner.UserName, pr.PR.Base.Repo.Name, pr.PR.Index)
				r, err := FetchGiteaReviews(gitea, reviewers, pr.PR.Base.Repo.Owner.UserName, pr.PR.Base.Repo.Name, pr.PR.Index)
				if err != nil {
					LogError("Cannot fetch gita reaviews for PR:", err)
					return false
				}
				pr.Reviews = r
				if !pr.Reviews.IsManualMergeOK() {
					LogInfo("Not approved manual merge. PR:", pr.PR.URL)
					return false
				}
			}

			is_manually_reviewed_ok = true
		}

		if !is_manually_reviewed_ok {
			LogInfo("manual merge not ok")
			return false
		}
	}

	for _, pr := range rs.PRs {
		var reviewers []string
		var pkg string
		if rs.IsPrjGitPR(pr.PR) {
			reviewers = configReviewers.Prj
			pkg = ""
		} else {
			reviewers = configReviewers.Pkg
			pkg = pr.PR.Base.Repo.Name
		}

		if strings.HasPrefix(pr.PR.Title, "WIP:") {
			LogInfo("WIP PR. Ignoring")
			return false
		}

		r, err := FetchGiteaReviews(gitea, reviewers, pr.PR.Base.Repo.Owner.UserName, pr.PR.Base.Repo.Name, pr.PR.Index)
		if err != nil {
			LogError("Cannot fetch gita reaviews for PR:", err)
			return false
		}

		is_manually_reviewed_ok = r.IsApproved()
		LogDebug(pr.PR.Base.Repo.Name, is_manually_reviewed_ok)
		if !is_manually_reviewed_ok {
			return false
		}

		if need_maintainer_review := !rs.IsPrjGitPR(pr.PR) || pr.PR.User.UserName != rs.BotUser; need_maintainer_review {
			if is_manually_reviewed_ok = maintainers.IsApproved(pkg, r.reviews, pr.PR.User.UserName); !is_manually_reviewed_ok {
				LogDebug(" not approved?", pkg)
				return false
			}
		} else {
			LogDebug("PrjGit PR -- bot created, no need for review")
		}
	}
	return is_manually_reviewed_ok
}

func (rs *PRSet) Merge(gitea GiteaReviewUnrequester, git Git) error {
	prjgit_info, err := rs.GetPrjGitPR()
	if err != nil {
		return err
	}
	prjgit := prjgit_info.PR

	_, _, prjgitBranch := rs.Config.GetPrjGit()
	remote, err := git.GitClone(DefaultGitPrj, prjgitBranch, prjgit.Base.Repo.SSHURL)
	PanicOnError(err)
	git.GitExecOrPanic(DefaultGitPrj, "fetch", remote, prjgit.Head.Sha)

	// if other changes merged, check if we have conflicts
	/*
		rev := strings.TrimSpace(git.GitExecWithOutputOrPanic(DefaultGitPrj, "merge-base", "HEAD", prjgit.Base.Sha, prjgit.Head.Sha))
		if rev != prjgit.Base.Sha {
			return fmt.Errorf("Base.Sha (%s) not yet merged into project-git. Aborting merge.", prjgit.Base.Sha)
		}
	*/
	/*
		rev := git.GitExecWithOutputOrPanic(common.DefaultGitPrj, "rev-list", "-1", "HEAD")
		if rev != prjgit.Base.Sha {
			panic("FIXME")
		}
	*/
	msg := fmt.Sprintf("Merging\n\nPR: %s/%s!%d", prjgit.Base.Repo.Owner.UserName, prjgit.Base.Repo.Name, prjgit.Index)

	err = git.GitExec(DefaultGitPrj, "merge", "--no-ff", "-m", msg, prjgit.Head.Sha)
	if err != nil {
		status, statusErr := git.GitStatus(DefaultGitPrj)
		if statusErr != nil {
			return fmt.Errorf("Failed to merge: %w . Status also failed: %w", err, statusErr)
		}

		// we can only resolve conflicts with .gitmodules
		for _, s := range status {
			if s.Status == GitStatus_Unmerged {
				panic("Can't handle conflicts yet")
				if s.Path != ".gitmodules" {
					return err
				}

				submodules, err := git.GitSubmoduleList(DefaultGitPrj, "MERGE_HEAD")
				if err != nil {
					return fmt.Errorf("Failed to fetch submodules during merge resolution: %w", err)
				}
				s1, err := git.GitExecWithOutput(DefaultGitPrj, "cat-file", "blob", s.States[0])
				if err != nil {
					return fmt.Errorf("Failed fetching data during .gitmodules merge resoulution: %w", err)
				}
				s2, err := git.GitExecWithOutput(DefaultGitPrj, "cat-file", "blob", s.States[1])
				if err != nil {
					return fmt.Errorf("Failed fetching data during .gitmodules merge resoulution: %w", err)
				}
				s3, err := git.GitExecWithOutput(DefaultGitPrj, "cat-file", "blob", s.States[2])
				if err != nil {
					return fmt.Errorf("Failed fetching data during .gitmodules merge resoulution: %w", err)
				}

				subs1, err := ParseSubmodulesFile(strings.NewReader(s1))
				if err != nil {
					return fmt.Errorf("Failed parsing submodule file [%s] in merge: %w", s.States[0], err)
				}
				subs2, err := ParseSubmodulesFile(strings.NewReader(s2))
				if err != nil {
					return fmt.Errorf("Failed parsing submodule file [%s] in merge: %w", s.States[0], err)
				}
				subs3, err := ParseSubmodulesFile(strings.NewReader(s3))
				if err != nil {
					return fmt.Errorf("Failed parsing submodule file [%s] in merge: %w", s.States[0], err)
				}

				// merge from subs3 (target), subs1 (orig), subs2 (2-nd base that is missing from target base)
				// this will update submodules
				mergedSubs := slices.Concat(subs1, subs2, subs3)

				var filteredSubs []Submodule = make([]Submodule, 0, max(len(subs1), len(subs2), len(subs3)))
			nextSub:
				for subName := range submodules {

					for i := range mergedSubs {
						if path.Base(mergedSubs[i].Path) == subName {
							filteredSubs = append(filteredSubs, mergedSubs[i])
							continue nextSub
						}
					}
					return fmt.Errorf("Cannot find submodule for path: %s", subName)
				}

				out, err := os.Create(path.Join(git.GetPath(), DefaultGitPrj, ".gitmodules"))
				if err != nil {
					return fmt.Errorf("Can't open .gitmodules for writing: %w", err)
				}
				if err = WriteSubmodules(filteredSubs, out); err != nil {
					return fmt.Errorf("Can't write .gitmodules: %w", err)
				}
				if out.Close(); err != nil {
					return fmt.Errorf("Can't close .gitmodules: %w", err)
				}

				git.GitExecOrPanic(DefaultGitPrj, "add", ".gitmodules")
				git.GitExecOrPanic(DefaultGitPrj, "-c", "core.editor=true", "merge", "--continue")
			}
		}
	}

	// FF all non-prj git and unrequest reviews.
	for _, prinfo := range rs.PRs {
		// remove pending review requests
		repo := prinfo.PR.Base.Repo
		head := prinfo.PR.Head
		id := prinfo.PR.Index

		reviewers := make([]string, len(prinfo.PR.RequestedReviewers))
		for idx := range prinfo.PR.RequestedReviewers {
			r := prinfo.PR.RequestedReviewers[idx]
			if r != nil {
				reviewers[idx] = r.UserName
			}
		}
		if err := gitea.UnrequestReview(repo.Owner.UserName, repo.Name, id, reviewers...); err != nil {
			LogError("Cannot unrequest reviews in PR:", repo.Owner.UserName, repo.Name, id, reviewers, ": ", err)
		}

		// PrjGit already merged above, so skip here.
		if rs.IsPrjGitPR(prinfo.PR) {
			continue
		}
		br := rs.Config.Branch
		if len(br) == 0 {
			// if branch is unspecified, take it from the PR as it
			// matches default branch already
			br = prinfo.PR.Base.Name
		} else if br != prinfo.PR.Base.Name {
			panic(prinfo.PR.Base.Name + " is expected to match " + br)
		}
		prinfo.RemoteName, err = git.GitClone(repo.Name, br, repo.SSHURL)
		PanicOnError(err)
		git.GitExecOrPanic(repo.Name, "fetch", prinfo.RemoteName, head.Sha)
		git.GitExecOrPanic(repo.Name, "merge", "--ff", head.Sha)

	}

	// push changes
	if !IsDryRun {
		git.GitExecOrPanic(DefaultGitPrj, "push", remote)
	} else {
		LogInfo("*** WOULD push", DefaultGitPrj, "changes to", remote)
	}
	for _, prinfo := range rs.PRs {
		if rs.IsPrjGitPR(prinfo.PR) {
			continue
		}
		repo := prinfo.PR.Base.Repo

		if !IsDryRun {
			git.GitExecOrPanic(repo.Name, "push", prinfo.RemoteName)
		} else {
			LogInfo("*** WOULD push", repo.Name, "to", prinfo.RemoteName)
		}
	}

	return nil
}