// Package webhook delivers repository event notifications to user-configured
// HTTP endpoints. It is the spindle-side successor to the appview webhook
// notifier: spindle owns webhook configuration and delivery, firing from the
// repo events it already ingests (push, pull_request:*, repository:renamed).
package webhook

import (
	"bytes"
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"sync"
	"time"

	"github.com/avast/retry-go/v4"
	"github.com/bluesky-social/indigo/atproto/syntax"
	"github.com/google/uuid"
	"tangled.org/core/api/tangled"
	"tangled.org/core/hostutil"
	"tangled.org/core/log"
	"tangled.org/core/spindle/db"
	"tangled.org/core/spindle/models"
)

const (
	deliveryWorkers   = 8
	deliveryQueueSize = 256
	deliveryRetention = 50
)

var errQueueSaturated = errors.New("delivery queue saturated")

type Service struct {
	db        *db.DB
	logger    *slog.Logger
	client    *http.Client
	jobs      chan deliveryJob
	wg        sync.WaitGroup
	closeOnce sync.Once
}

func New(database *db.DB, dev bool) *Service {
	s := &Service{
		db:     database,
		logger: log.New("webhook"),
		// user-supplied webhook URLs are untrusted: block internal address
		// ranges and don't follow redirects to guard against SSRF.
		client: hostutil.SafeClient(dev, 30*time.Second),
		jobs:   make(chan deliveryJob, deliveryQueueSize),
	}
	for range deliveryWorkers {
		s.wg.Add(1)
		go s.worker()
	}
	return s
}

// FirePush delivers a push (git ref-update) event to subscribed webhooks.
func (s *Service) FirePush(ctx context.Context, repo *db.Repo, committerDid, ref, oldSha, newSha string) {
	webhooks := s.activeWebhooksForEvent(repo.RepoDid, models.WebhookEventPush)
	if len(webhooks) == 0 {
		return
	}

	pusher := committerDid
	if pusher == "" {
		pusher = repo.Owner.String()
	}
	payload := &models.WebhookPayload{
		Ref:        ref,
		Before:     oldSha,
		After:      newSha,
		Repository: buildRepository(repo),
		Pusher:     models.WebhookUser{Did: pusher},
	}
	payloadBytes, err := json.Marshal(payload)
	if err != nil {
		s.logger.Error("failed to marshal push payload", "repo_did", repo.RepoDid, "err", err)
		return
	}

	userAgent := "Tangled-Hook/push"
	if len(newSha) >= 7 {
		userAgent = "Tangled-Hook/" + newSha[:7]
	}
	for _, webhook := range webhooks {
		s.dispatch(deliveryJob{ctx: ctx, webhook: webhook, event: string(models.WebhookEventPush), repoFullName: payload.Repository.FullName, userAgent: userAgent, payload: payloadBytes})
	}
}

// FireRename delivers a repository:renamed event to subscribed webhooks.
func (s *Service) FireRename(ctx context.Context, actor syntax.DID, repo *db.Repo, oldName, newName string) {
	webhooks := s.activeWebhooksForEvent(repo.RepoDid, models.WebhookEventRepoRenamed)
	if len(webhooks) == 0 {
		return
	}

	payload := &models.WebhookRenamePayload{
		OldName:    oldName,
		NewName:    newName,
		Repository: buildRepository(repo),
		Sender:     models.WebhookUser{Did: actor.String()},
	}
	payloadBytes, err := json.Marshal(payload)
	if err != nil {
		s.logger.Error("failed to marshal rename payload", "repo_did", repo.RepoDid, "err", err)
		return
	}

	for _, webhook := range webhooks {
		s.dispatch(deliveryJob{ctx: ctx, webhook: webhook, event: string(models.WebhookEventRepoRenamed), repoFullName: payload.Repository.FullName, userAgent: "Tangled-Hook/rename", payload: payloadBytes})
	}
}

// FirePullRequest delivers a pull_request:* event to subscribed webhooks. repo
// is the target repository; record is the pull record; pullAuthor authored the
// pull; sender is the actor that triggered this transition (equal to pullAuthor
// for created/resubmitted).
func (s *Service) FirePullRequest(ctx context.Context, event models.WebhookEvent, action string, repo *db.Repo, record *tangled.RepoPull, pullAuthor, sender syntax.DID) {
	// pull request events may originate from firehose handlers whose context is
	// canceled promptly; detach so in-flight deliveries are not cut short
	ctx = context.WithoutCancel(ctx)

	webhooks := s.activeWebhooksForEvent(repo.RepoDid, event)
	if len(webhooks) == 0 {
		return
	}

	pr := models.WebhookPullRequest{
		Title:       record.Title,
		State:       pullStateFromAction(action),
		RoundNumber: len(record.Rounds),
		Owner:       models.WebhookUser{Did: pullAuthor.String()},
		CreatedAt:   record.CreatedAt,
	}
	if record.Body != nil {
		pr.Body = *record.Body
	}
	if record.Target != nil {
		pr.TargetBranch = record.Target.Branch
	}
	if record.Source != nil {
		source := &models.WebhookPullRequestSource{Branch: record.Source.Branch}
		if record.Source.Repo != nil {
			source.Repo = *record.Source.Repo
		}
		pr.Source = source
	}

	payload := &models.WebhookPullRequestPayload{
		Action:      action,
		PullRequest: pr,
		Repository:  buildRepository(repo),
		Sender:      models.WebhookUser{Did: sender.String()},
	}
	payloadBytes, err := json.Marshal(payload)
	if err != nil {
		s.logger.Error("failed to marshal pull request payload", "repo_did", repo.RepoDid, "err", err)
		return
	}

	for _, webhook := range webhooks {
		s.dispatch(deliveryJob{ctx: ctx, webhook: webhook, event: string(event), repoFullName: payload.Repository.FullName, userAgent: "Tangled-Hook/pull_request", payload: payloadBytes})
	}
}

// Redeliver re-sends a stored delivery via the live send-and-record path,
// signing with the webhook's current secret.
func (s *Service) Redeliver(ctx context.Context, webhook models.Webhook, prev models.WebhookDelivery) {
	// recover the repo full name (X-Tangled-Repo header) from the stored payload
	var meta struct {
		Repository struct {
			FullName string `json:"full_name"`
		} `json:"repository"`
	}
	_ = json.Unmarshal([]byte(prev.RequestBody), &meta)

	s.dispatch(deliveryJob{ctx: ctx, webhook: webhook, event: prev.Event, repoFullName: meta.Repository.FullName, userAgent: "Tangled-Hook/retry", payload: []byte(prev.RequestBody)})
}

// pullStateFromAction derives the pull request state carried in the payload
// from the lifecycle action, since the pull record does not store state.
func pullStateFromAction(action string) string {
	switch action {
	case "merged":
		return "merged"
	case "closed":
		return "closed"
	default: // created, resubmitted, reopened
		return "open"
	}
}

func (s *Service) activeWebhooksForEvent(repoDid syntax.DID, event models.WebhookEvent) []models.Webhook {
	webhooks, err := s.db.GetActiveWebhooksForRepo(repoDid)
	if err != nil {
		s.logger.Error("failed to get webhooks for repo", "repo_did", repoDid, "err", err)
		return nil
	}
	var matching []models.Webhook
	for _, webhook := range webhooks {
		if webhook.HasEvent(event) {
			matching = append(matching, webhook)
		}
	}
	return matching
}

func buildRepository(repo *db.Repo) models.WebhookRepository {
	owner := repo.Owner.String()
	rkey := repo.Rkey.String()
	return models.WebhookRepository{
		Name:      repo.Name,
		FullName:  fmt.Sprintf("%s/%s", owner, rkey),
		HtmlUrl:   fmt.Sprintf("https://%s/%s/%s", repo.Knot, owner, rkey),
		CloneUrl:  fmt.Sprintf("https://%s/%s/%s", repo.Knot, owner, rkey),
		SshUrl:    fmt.Sprintf("ssh://git@%s/%s/%s", repo.Knot, owner, rkey),
		CreatedAt: repo.CreatedAt,
		UpdatedAt: repo.CreatedAt,
		Owner:     models.WebhookUser{Did: owner},
	}
}

type deliveryJob struct {
	ctx          context.Context
	webhook      models.Webhook
	event        string
	repoFullName string
	userAgent    string
	payload      []byte
}

func (s *Service) dispatch(job deliveryJob) {
	select {
	case s.jobs <- job:
	default:
		s.logger.Warn("webhook delivery queue saturated", "webhook_id", job.webhook.Id, "url", job.webhook.Url)
		s.record(&models.WebhookDelivery{
			WebhookId:    job.webhook.Id,
			Event:        job.event,
			DeliveryId:   uuid.New().String(),
			Url:          job.webhook.Url,
			RequestBody:  string(job.payload),
			ResponseBody: errQueueSaturated.Error(),
		})
	}
}

func (s *Service) worker() {
	defer s.wg.Done()
	for job := range s.jobs {
		s.sendWebhook(job)
	}
}

func (s *Service) Close(ctx context.Context) {
	s.closeOnce.Do(func() { close(s.jobs) })
	done := make(chan struct{})
	go func() {
		s.wg.Wait()
		close(done)
	}()
	select {
	case <-done:
	case <-ctx.Done():
		s.logger.Warn("webhook deliveries still in flight at shutdown")
	}
}

func (s *Service) sendWebhook(job deliveryJob) {
	ctx := job.ctx

	var signature string
	if job.webhook.Secret != "" {
		signature = "sha256=" + s.computeSignature(job.payload, job.webhook.Secret)
	}

	deliveryId := uuid.New().String()

	retryOpts := []retry.Option{
		retry.Attempts(3),
		retry.Delay(1 * time.Second),
		retry.MaxDelay(10 * time.Second),
		retry.DelayType(retry.BackOffDelay),
		retry.LastErrorOnly(true),
		retry.OnRetry(func(n uint, err error) {
			s.logger.Info("retrying webhook delivery", "webhook_id", job.webhook.Id, "attempt", n+1, "err", err)
		}),
		retry.Context(ctx),
	}

	var (
		resp         *http.Response
		lastStatus   int
		lastResponse string
	)
	err := retry.Do(func() error {
		// build a fresh request each attempt so the body reader is not
		// exhausted after the first try
		req, err := http.NewRequestWithContext(ctx, "POST", job.webhook.Url, bytes.NewReader(job.payload))
		if err != nil {
			return retry.Unrecoverable(err)
		}
		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("User-Agent", job.userAgent)
		req.Header.Set("X-Tangled-Event", job.event)
		req.Header.Set("X-Tangled-Hook-ID", fmt.Sprintf("%d", job.webhook.Id))
		req.Header.Set("X-Tangled-Delivery", deliveryId)
		req.Header.Set("X-Tangled-Repo", job.repoFullName)
		if signature != "" {
			req.Header.Set("X-Tangled-Signature-256", signature)
		}

		r, err := s.client.Do(req)
		if err != nil {
			return err
		}
		lastStatus = r.StatusCode
		body, readErr := io.ReadAll(io.LimitReader(r.Body, 10*1024))
		r.Body.Close()
		if readErr != nil {
			s.logger.Warn("failed to read webhook response body", "webhook_id", job.webhook.Id, "err", readErr)
		}
		lastResponse = string(body)
		if r.StatusCode >= 500 {
			return fmt.Errorf("server error: %d", r.StatusCode)
		}
		resp = r
		return nil
	}, retryOpts...)

	delivery := &models.WebhookDelivery{
		WebhookId:    job.webhook.Id,
		Event:        job.event,
		DeliveryId:   deliveryId,
		Url:          job.webhook.Url,
		RequestBody:  string(job.payload),
		ResponseCode: lastStatus,
		ResponseBody: lastResponse,
	}

	switch {
	case err != nil:
		s.logger.Error("webhook request failed after retries", "webhook_id", job.webhook.Id, "err", err)
		delivery.ResponseBody = err.Error()
	case resp != nil && resp.StatusCode >= 200 && resp.StatusCode < 300:
		delivery.Success = true
		s.logger.Info("webhook delivered successfully", "webhook_id", job.webhook.Id, "url", job.webhook.Url, "delivery_id", deliveryId)
	default:
		s.logger.Warn("webhook delivery failed", "webhook_id", job.webhook.Id, "status", lastStatus, "url", job.webhook.Url)
	}

	s.record(delivery)
}

func (s *Service) record(delivery *models.WebhookDelivery) {
	if err := s.db.AddWebhookDelivery(delivery); err != nil {
		s.logger.Error("failed to record webhook delivery", "webhook_id", delivery.WebhookId, "err", err)
		return
	}
	if err := s.db.PruneWebhookDeliveries(delivery.WebhookId, deliveryRetention); err != nil {
		s.logger.Error("failed to prune webhook deliveries", "webhook_id", delivery.WebhookId, "err", err)
	}
}

func (s *Service) computeSignature(payload []byte, secret string) string {
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(payload)
	return hex.EncodeToString(mac.Sum(nil))
}