package lanematerialize

import (
	"context"
	"fmt"
	"sort"
	"strings"

	"inbox/internal/app/lanegit"
	"inbox/internal/base/timeutil"
	"inbox/internal/domain/lane"
	"inbox/internal/domain/lanesync"
)

type SyncRecorder interface {
	CreateLaneSync(ctx context.Context, value lanesync.Record) (lanesync.Record, error)
}

type Upstream struct {
	TaskID string
	Lane   lane.Record
}

type Service struct {
	recorder SyncRecorder
	runner   lanegit.Runner
	clock    timeutil.Clock
}

func NewService(recorder SyncRecorder, runner lanegit.Runner, clock timeutil.Clock) *Service {
	if runner == nil {
		runner = lanegit.ExecRunner{}
	}
	if clock == nil {
		clock = timeutil.SystemClock{}
	}
	return &Service{recorder: recorder, runner: runner, clock: clock}
}

func (s *Service) Materialize(ctx context.Context, downstream lane.Record, taskID string, upstreams []Upstream) error {
	if len(upstreams) == 0 {
		return nil
	}
	worktree := strings.TrimSpace(downstream.WorktreePath)
	if worktree == "" {
		return fmt.Errorf("lane %s has empty worktree path", downstream.ID)
	}
	clean, err := s.isClean(ctx, worktree)
	if err != nil {
		return err
	}
	if !clean {
		return fmt.Errorf("lane %s worktree has uncommitted changes before materialization", downstream.ID)
	}

	sort.SliceStable(upstreams, func(i, j int) bool {
		if upstreams[i].Lane.ID == upstreams[j].Lane.ID {
			return upstreams[i].TaskID < upstreams[j].TaskID
		}
		return upstreams[i].Lane.ID < upstreams[j].Lane.ID
	})

	for _, upstream := range upstreams {
		if upstream.Lane.ID == downstream.ID {
			continue
		}
		commit := strings.TrimSpace(upstream.Lane.HeadCommit)
		if commit == "" {
			err := fmt.Errorf("upstream lane %s has no head_commit", upstream.Lane.ID)
			s.record(ctx, downstream, upstream, "", lanesync.StatusFailed, err.Error())
			return err
		}

		alreadyMerged, err := s.isAncestor(ctx, worktree, commit)
		if err != nil {
			s.record(ctx, downstream, upstream, "", lanesync.StatusFailed, err.Error())
			return err
		}
		if alreadyMerged {
			s.record(ctx, downstream, upstream, commit, lanesync.StatusSkipped, "")
			continue
		}

		if _, err := lanegit.Run(ctx, s.runner, worktree, nil, "merge", "--no-ff", "--no-edit", commit); err != nil {
			_ = s.abortMerge(ctx, worktree)
			s.record(ctx, downstream, upstream, "", lanesync.StatusFailed, err.Error())
			return err
		}
		mergedHead, err := s.headCommit(ctx, worktree)
		if err != nil {
			s.record(ctx, downstream, upstream, "", lanesync.StatusFailed, err.Error())
			return err
		}
		s.record(ctx, downstream, upstream, mergedHead, lanesync.StatusApplied, "")
	}
	return nil
}

func (s *Service) record(ctx context.Context, downstream lane.Record, upstream Upstream, mergeCommit string, status lanesync.Status, errorMessage string) {
	if s.recorder == nil {
		return
	}
	_, _ = s.recorder.CreateLaneSync(ctx, lanesync.Record{
		WorkspaceID:      downstream.WorkspaceID,
		TopicID:          downstream.TopicID,
		DownstreamLaneID: downstream.ID,
		UpstreamLaneID:   upstream.Lane.ID,
		TaskID:           upstream.TaskID,
		UpstreamCommit:   strings.TrimSpace(upstream.Lane.HeadCommit),
		MergeCommit:      strings.TrimSpace(mergeCommit),
		Status:           status,
		ErrorMessage:     strings.TrimSpace(errorMessage),
	})
}

func (s *Service) abortMerge(ctx context.Context, worktree string) error {
	_, err := lanegit.Run(ctx, s.runner, worktree, nil, "merge", "--abort")
	return err
}

func (s *Service) headCommit(ctx context.Context, worktree string) (string, error) {
	out, err := lanegit.Run(ctx, s.runner, worktree, nil, "rev-parse", "HEAD")
	if err != nil {
		return "", err
	}
	return strings.TrimSpace(out), nil
}

func (s *Service) isClean(ctx context.Context, worktree string) (bool, error) {
	out, err := lanegit.Run(ctx, s.runner, worktree, nil, "status", "--porcelain")
	if err != nil {
		return false, err
	}
	return strings.TrimSpace(out) == "", nil
}

func (s *Service) isAncestor(ctx context.Context, worktree, commit string) (bool, error) {
	head, err := s.headCommit(ctx, worktree)
	if err != nil {
		return false, err
	}
	_, err = s.runner.Run(ctx, worktree, nil, "git", "merge-base", "--is-ancestor", commit, head)
	if err == nil {
		return true, nil
	}
	if lanegit.IsExitCode(err, 1) {
		return false, nil
	}
	return false, fmt.Errorf("git merge-base --is-ancestor %s %s: %w", commit, head, err)
}