Add Go CDN and playground server

Build Core and Handles into in-memory CDN modules, add the marketing site and tutorial docs, and provide a SQLite-backed WebGPU playground with TypeScript tooling and profiling.

Amp-Thread-ID: https://ampcode.com/threads/T-01a02485-5574-707c-bff4-5668d83bee8a
Co-authored-by: Heaust Azure <heaust.azure@gmail.com>

server/database.go

@@ -0,0 +1,153 @@
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"database/sql"
+	"errors"
+	"fmt"
+	"math/big"
+	"os"
+	"path/filepath"
+	"regexp"
+	"time"
+	"unicode/utf8"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+const (
+	maximumCodeBytes  = 200 * 1024
+	maximumTitleRunes = 80
+)
+
+var playgroundIDPattern = regexp.MustCompile(`^[a-z0-9]{6,24}$`)
+
+type playground struct {
+	ID        string    `json:"id"`
+	Revision  int       `json:"revision"`
+	Title     string    `json:"title"`
+	Code      string    `json:"code"`
+	CreatedAt time.Time `json:"createdAt"`
+}
+
+type playgroundStore struct {
+	*sql.DB
+}
+
+func openPlaygroundStore(path string) (*playgroundStore, error) {
+	if path != ":memory:" {
+		if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+			return nil, err
+		}
+	}
+	database, err := sql.Open("sqlite3", path+"?_foreign_keys=on&_busy_timeout=5000&_journal_mode=WAL")
+	if err != nil {
+		return nil, err
+	}
+	database.SetMaxOpenConns(1)
+	store := &playgroundStore{DB: database}
+	if err := store.initialize(); err != nil {
+		database.Close()
+		return nil, err
+	}
+	return store, nil
+}
+
+func (store *playgroundStore) initialize() error {
+	_, err := store.Exec(`
+		CREATE TABLE IF NOT EXISTS playgrounds (
+			id TEXT NOT NULL,
+			revision INTEGER NOT NULL CHECK (revision > 0),
+			title TEXT NOT NULL,
+			code TEXT NOT NULL,
+			created_at TEXT NOT NULL,
+			PRIMARY KEY (id, revision)
+		);
+		CREATE INDEX IF NOT EXISTS playgrounds_created_at
+			ON playgrounds (created_at DESC);
+	`)
+	return err
+}
+
+func (store *playgroundStore) save(ctx context.Context, id, title, code string) (playground, error) {
+	if id != "" && !playgroundIDPattern.MatchString(id) {
+		return playground{}, errors.New("invalid playground id")
+	}
+	if title == "" || utf8.RuneCountInString(title) > maximumTitleRunes {
+		return playground{}, fmt.Errorf("title must contain 1 to %d characters", maximumTitleRunes)
+	}
+	if code == "" || len(code) > maximumCodeBytes || !utf8.ValidString(code) {
+		return playground{}, fmt.Errorf("code must contain 1 to %d bytes of UTF-8", maximumCodeBytes)
+	}
+	if id == "" {
+		var err error
+		id, err = randomPlaygroundID()
+		if err != nil {
+			return playground{}, err
+		}
+	}
+
+	transaction, err := store.BeginTx(ctx, nil)
+	if err != nil {
+		return playground{}, err
+	}
+	defer transaction.Rollback()
+
+	var revision int
+	if err := transaction.QueryRowContext(
+		ctx,
+		`SELECT COALESCE(MAX(revision), 0) + 1 FROM playgrounds WHERE id = ?`,
+		id,
+	).Scan(&revision); err != nil {
+		return playground{}, err
+	}
+	createdAt := time.Now().UTC().Truncate(time.Millisecond)
+	if _, err := transaction.ExecContext(
+		ctx,
+		`INSERT INTO playgrounds (id, revision, title, code, created_at) VALUES (?, ?, ?, ?, ?)`,
+		id,
+		revision,
+		title,
+		code,
+		createdAt.Format(time.RFC3339Nano),
+	); err != nil {
+		return playground{}, err
+	}
+	if err := transaction.Commit(); err != nil {
+		return playground{}, err
+	}
+	return playground{ID: id, Revision: revision, Title: title, Code: code, CreatedAt: createdAt}, nil
+}
+
+func (store *playgroundStore) get(ctx context.Context, id string, revision int) (playground, error) {
+	if !playgroundIDPattern.MatchString(id) || revision < 1 {
+		return playground{}, sql.ErrNoRows
+	}
+	var result playground
+	var createdAt string
+	err := store.QueryRowContext(
+		ctx,
+		`SELECT id, revision, title, code, created_at FROM playgrounds WHERE id = ? AND revision = ?`,
+		id,
+		revision,
+	).Scan(&result.ID, &result.Revision, &result.Title, &result.Code, &createdAt)
+	if err != nil {
+		return playground{}, err
+	}
+	result.CreatedAt, err = time.Parse(time.RFC3339Nano, createdAt)
+	return result, err
+}
+
+func randomPlaygroundID() (string, error) {
+	const alphabet = "abcdefghijkmnopqrstuvwxyz23456789"
+	result := make([]byte, 10)
+	for index := range result {
+		value, err := rand.Int(rand.Reader, big.NewInt(int64(len(alphabet))))
+		if err != nil {
+			return "", err
+		}
+		result[index] = alphabet[value.Int64()]
+	}
+	return string(result), nil
+}