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package server

import (
	"crypto/hmac"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"io"
	"log"
	"net/http"
	"strings"
	"time"

	"custard/internal/release"
)

// hookPayload is the subset of Soft Serve's webhook JSON we use.
type hookPayload struct {
	Event      string `json:"event"`
	Repository struct {
		Name        string `json:"name"`
		Description string `json:"description"`
		Private     bool   `json:"private"`
	} `json:"repository"`
	Ref     string `json:"ref"`
	Created bool   `json:"created"`
	Deleted bool   `json:"deleted"`
}

// handleReleaseHook receives Soft Serve's branch_tag_create webhook and, for a
// brew-enabled public repo tagged vX.Y.Z, publishes a formula to the tap.
// Disabled (404) unless a webhook secret is configured.
func (s *Server) handleReleaseHook(w http.ResponseWriter, r *http.Request) {
	if s.cfg.WebhookSecret == "" {
		s.notFound(w, r)
		return
	}
	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20))
	if err != nil {
		http.Error(w, "bad request", http.StatusBadRequest)
		return
	}
	if !validSignature(r.Header.Get("X-Softserve-Signature"), body, s.cfg.WebhookSecret) {
		http.Error(w, "bad signature", http.StatusUnauthorized)
		return
	}

	var p hookPayload
	if err := json.Unmarshal(body, &p); err != nil {
		http.Error(w, "bad payload", http.StatusBadRequest)
		return
	}

	// Only act on a newly-created tag.
	tag := strings.TrimPrefix(p.Ref, "refs/tags/")
	skip := ""
	switch {
	case p.Event != "branch_tag_create" || !p.Created || p.Deleted:
		skip = "not a tag-create"
	case tag == p.Ref:
		skip = "not a tag"
	case !release.IsReleaseTag(tag):
		skip = "not a semver release tag"
	case p.Repository.Private:
		skip = "private repo"
	}
	log.Printf("hook: repo=%s ref=%q event=%s created=%v deleted=%v", p.Repository.Name, p.Ref, p.Event, p.Created, p.Deleted)
	if skip != "" {
		log.Printf("hook: ignored (%s) repo=%s tag=%s", skip, p.Repository.Name, tag)
		writeText(w, http.StatusAccepted, "ignored: "+skip)
		return
	}

	// Publish in the background: respond now so we don't hold Soft Serve's
	// delivery connection while git finishes migrating the pushed objects (the
	// new tag can take several seconds to become readable by a fresh git open).
	repo := p.Repository.Name
	go s.publishRelease(repo, tag, p.Repository.Description)
	writeText(w, http.StatusAccepted, "accepted: "+repo+" "+tag)
}

// publishRelease reads the repo's opt-in config (retrying while the freshly
// pushed tag becomes readable) and, if brew-enabled, publishes to the tap.
func (s *Server) publishRelease(repo, tag, desc string) {
	var cfg release.RepoConfig
	var ok bool
	for i := 0; i < 30; i++ {
		if cfg, ok = release.ReadRepoConfig(s.store, repo, tag); ok {
			break
		}
		time.Sleep(time.Second)
	}
	if !ok {
		log.Printf("hook: %s@%s — config never became readable; giving up", repo, tag)
		return
	}
	if !cfg.Brew.Enabled {
		log.Printf("hook: ignored (not brew-enabled) repo=%s tag=%s", repo, tag)
		return
	}
	ver, err := release.Publish(release.Options{
		Store:     s.store,
		ReposPath: s.cfg.ReposPath,
		DLPath:    s.cfg.DLPath,
		TapRepo:   s.cfg.TapRepo,
		BaseURL:   s.cfg.BaseURL,
		Repo:      repo,
		Tag:       tag,
		Desc:      desc,
		Package:   cfg.Brew.Package,
	})
	if err != nil {
		log.Printf("release %s@%s failed: %v", repo, tag, err)
		return
	}
	log.Printf("released %s %s to tap", repo, ver)
}

// validSignature checks the "sha256=<hex>" HMAC over the raw body.
func validSignature(header string, body []byte, secret string) bool {
	want, ok := strings.CutPrefix(header, "sha256=")
	if !ok {
		return false
	}
	mac := hmac.New(sha256.New, []byte(secret))
	mac.Write(body)
	got := hex.EncodeToString(mac.Sum(nil))
	return hmac.Equal([]byte(got), []byte(want))
}

func writeText(w http.ResponseWriter, code int, msg string) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.WriteHeader(code)
	_, _ = io.WriteString(w, msg+"\n")
}