feat. rebuild service in Go

Rebuild the Gitea Codex review bot from the product contract with a Go HTTP service, durable SQL queue, typed Gitea client, isolated runner, and deployment updates.

Co-Authored-By: Claude <noreply@anthropic.com>

internal/webhook/webhook.go

@@ -0,0 +1,127 @@
+package webhook
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"gitea-codex-bot/internal/domain"
+)
+
+func VerifySignature(body []byte, secret, supplied string) bool {
+	supplied = strings.TrimSpace(strings.TrimPrefix(strings.TrimSpace(supplied), "sha256="))
+	if supplied == "" {
+		return false
+	}
+	mac := hmac.New(sha256.New, []byte(secret))
+	_, _ = mac.Write(body)
+	expected := hex.EncodeToString(mac.Sum(nil))
+	return hmac.Equal([]byte(strings.ToLower(expected)), []byte(strings.ToLower(supplied)))
+}
+
+func Digest(body []byte) string { sum := sha256.Sum256(body); return hex.EncodeToString(sum[:]) }
+
+func ParseEvent(eventName, delivery string, body []byte) (domain.WebhookEvent, error) {
+	if eventName != "issue_comment" && eventName != "pull_request_comment" {
+		return domain.WebhookEvent{}, errors.New("event ignored")
+	}
+	var raw map[string]any
+	if err := json.Unmarshal(body, &raw); err != nil {
+		return domain.WebhookEvent{}, errors.New("invalid JSON payload")
+	}
+	repo := nestedString(raw, "repository", "full_name")
+	commentID := nestedInt64(raw, "comment", "id")
+	sender := nestedString(raw, "sender", "username")
+	commentBody := nestedString(raw, "comment", "body")
+	if repo == "" || commentID <= 0 {
+		return domain.WebhookEvent{}, errors.New("not a pull request comment")
+	}
+	prNumber, headSHA := 0, ""
+	if eventName == "issue_comment" {
+		if _, ok := raw["pull_request"]; !ok || raw["pull_request"] == nil {
+			return domain.WebhookEvent{}, errors.New("not a pull request comment")
+		}
+		issue, ok := raw["issue"].(map[string]any)
+		if !ok || !truthy(issue["pull_request"]) {
+			return domain.WebhookEvent{}, errors.New("not a pull request comment")
+		}
+		prNumber = number(issue["number"])
+		headSHA = nestedString(raw, "pull_request", "head", "sha")
+	} else {
+		pr, ok := raw["pull_request"].(map[string]any)
+		if !ok || pr == nil {
+			return domain.WebhookEvent{}, errors.New("not a pull request comment")
+		}
+		prNumber = number(pr["number"])
+		headSHA = nestedString(raw, "pull_request", "head", "sha")
+	}
+	if prNumber <= 0 {
+		return domain.WebhookEvent{}, errors.New("not a pull request comment")
+	}
+	if headSHA == "" {
+		headSHA = "unknown"
+	}
+	return domain.WebhookEvent{EventName: eventName, DeliveryID: delivery, Repo: repo, PRNumber: prNumber, HeadSHA: headSHA, CommentID: commentID, CommentBody: strings.TrimSpace(commentBody), Sender: sender, PayloadSHA256: Digest(body)}, nil
+}
+
+func nestedString(raw map[string]any, path ...string) string {
+	var current any = raw
+	for _, key := range path {
+		obj, ok := current.(map[string]any)
+		if !ok {
+			return ""
+		}
+		current = obj[key]
+	}
+	if value, ok := current.(string); ok {
+		return value
+	}
+	return ""
+}
+func nestedInt64(raw map[string]any, path ...string) int64 {
+	var current any = raw
+	for _, key := range path {
+		obj, ok := current.(map[string]any)
+		if !ok {
+			return 0
+		}
+		current = obj[key]
+	}
+	return int64(number(current))
+}
+func number(value any) int {
+	switch v := value.(type) {
+	case float64:
+		return int(v)
+	case json.Number:
+		n, _ := strconv.Atoi(string(v))
+		return n
+	case int:
+		return v
+	case int64:
+		return int(v)
+	case string:
+		n, _ := strconv.Atoi(v)
+		return n
+	}
+	return 0
+}
+func truthy(value any) bool {
+	switch v := value.(type) {
+	case bool:
+		return v
+	case map[string]any:
+		return len(v) > 0
+	case string:
+		return strings.TrimSpace(v) != ""
+	default:
+		return value != nil
+	}
+}
+
+var _ = fmt.Sprintf