t5de-catalog: store and serve community product files

A Go server that takes product uploads with hub upload tokens, checks them by
t5de-api's pack rules, stores files by sha256, registers revisions with the hub
(POST /api/v1/catalog/revisions), and serves files with immutable caching;
files used only by adult revisions need an adult access token. Contract:
t5de-hub's docs/products.md.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

internal/hub/hub.go

@@ -0,0 +1,113 @@
+// Package hub is the catalog's client for T5DE's hub (server to server, docs/products.md "For catalogs").
+package hub
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strings"
+	"time"
+
+	"git.t5de.dev/t5de/t5de-catalog/internal/store"
+)
+
+// Client calls the hub as one catalog.
+type Client struct {
+	url    string
+	auth   string
+	client *http.Client
+}
+
+// New returns a client for the hub at hubURL (its API), as catalog id with its key. client may be nil.
+func New(hubURL, id, key string, client *http.Client) *Client {
+	if client == nil {
+		client = &http.Client{Timeout: 60 * time.Second}
+	}
+	return &Client{url: strings.TrimRight(hubURL, "/"), auth: "Catalog " + id + ":" + key, client: client}
+}
+
+// NewRevision is what the catalog registers.
+type NewRevision struct {
+	UploadToken string       `json:"uploadToken"`
+	Files       []store.File `json:"files"`
+	Rating      string       `json:"rating"`
+	Parent      int64        `json:"parent"`
+	Name        string       `json:"name"`
+	Notes       string       `json:"notes"`
+}
+
+// Registered is the hub's answer.
+type Registered struct {
+	Product  string `json:"product"`
+	Revision int    `json:"revision"`
+}
+
+// Error is the hub refusing a request: its status and, when it sent them, its error code and message.
+type Error struct {
+	Status  int
+	Code    string
+	Message string
+}
+
+func (e *Error) Error() string {
+	if e.Code != "" {
+		return fmt.Sprintf("hub: %d %s: %s", e.Status, e.Code, e.Message)
+	}
+	return fmt.Sprintf("hub: %d", e.Status)
+}
+
+var productID = regexp.MustCompile(`^[a-z2-7]{10}$`)
+
+// ValidProduct reports whether s is a product ID (10 of a-z2-7).
+func ValidProduct(s string) bool { return productID.MatchString(s) }
+
+// RegisterRevision posts a revision to the hub (POST /api/v1/catalog/revisions). A refusal is an *Error; other
+// errors mean the hub couldn't be reached or answered nonsense.
+func (c *Client) RegisterRevision(ctx context.Context, r NewRevision) (*Registered, error) {
+	if r.Files == nil {
+		r.Files = []store.File{}
+	}
+	body, err := json.Marshal(r)
+	if err != nil {
+		return nil, err
+	}
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.url+"/api/v1/catalog/revisions", bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Authorization", c.auth)
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "application/json")
+	resp, err := c.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	data, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
+	if err != nil {
+		return nil, err
+	}
+	if resp.StatusCode != http.StatusCreated && resp.StatusCode != http.StatusOK {
+		e := &Error{Status: resp.StatusCode}
+		var msg struct {
+			Error   string `json:"error"`
+			Message string `json:"message"`
+		}
+		if json.Unmarshal(data, &msg) == nil {
+			e.Code, e.Message = msg.Error, msg.Message
+		}
+		return nil, e
+	}
+	var reg Registered
+	if err := json.Unmarshal(data, &reg); err != nil {
+		return nil, fmt.Errorf("hub: bad answer: %v", err)
+	}
+	if !ValidProduct(reg.Product) || reg.Revision < 1 {
+		return nil, fmt.Errorf("hub: bad answer: product %q, revision %d", reg.Product, reg.Revision)
+	}
+	return &reg, nil
+}