Implement post.Store

5 files changed, 713 insertions, 39 deletions

diff --git a/srv/src/mailinglist/store.go b/srv/src/mailinglist/store.go
index f9790c0..a7a210f 100644
--- a/srv/src/mailinglist/store.go
+++ b/srv/src/mailinglist/store.go
@@ -83,7 +83,8 @@ type store struct {
 	db *sql.DB
 }
 
-// NewStore initializes a new store using the given SQL DB instance.
+// NewStore initializes a new Store using a sqlite3 database at the given file
+// path.
 func NewStore(dbFile string) (Store, error) {
 
 	db, err := sql.Open("sqlite3", dbFile)
diff --git a/srv/src/post/date.go b/srv/src/post/date.go
new file mode 100644
index 0000000..34fe109
--- /dev/null
+++ b/srv/src/post/date.go
@@ -0,0 +1,59 @@
+package post
+
+import (
+	"database/sql/driver"
+	"fmt"
+	"time"
+)
+
+// Date represents a calendar date with no timezone information attached.
+type Date struct {
+	Year  int
+	Month time.Month
+	Day   int
+}
+
+// DateFromTime converts a Time into a Date, truncating all non-date
+// information.
+func DateFromTime(t time.Time) Date {
+	t = t.UTC()
+	return Date{
+		Year:  t.Year(),
+		Month: t.Month(),
+		Day:   t.Day(),
+	}
+}
+
+// ToTime converts a Date into a Time. The returned time will be UTC midnight of
+// the Date.
+func (d *Date) ToTime() time.Time {
+	return time.Date(d.Year, d.Month, d.Day, 0, 0, 0, 0, time.UTC)
+}
+
+// Scan implements the sql.Scanner interface.
+func (d *Date) Scan(src interface{}) error {
+
+	if src == nil {
+		*d = Date{}
+		return nil
+	}
+
+	ts, ok := src.(int64)
+
+	if !ok {
+		return fmt.Errorf("cannot scan value %#v into Date", src)
+	}
+
+	*d = DateFromTime(time.Unix(ts, 0))
+	return nil
+}
+
+// Value implements the driver.Valuer interface.
+func (d Date) Value() (driver.Value, error) {
+
+	if d == (Date{}) {
+		return nil, nil
+	}
+
+	return d.ToTime().Unix(), nil
+}
diff --git a/srv/src/post/post.go b/srv/src/post/post.go
index 54555c3..7803c82 100644
--- a/srv/src/post/post.go
+++ b/srv/src/post/post.go
@@ -2,30 +2,10 @@
 package post
 
 import (
-	"fmt"
-	"path"
 	"regexp"
 	"strings"
-	"time"
 )
 
-// Date represents a calendar date with no timezone information attached.
-type Date struct {
-	Year  int
-	Month time.Month
-	Day   int
-}
-
-// DateFromTime converts a Time into a Date, truncating all non-date
-// information.
-func DateFromTime(t time.Time) Date {
-	return Date{
-		Year:  t.Year(),
-		Month: t.Month(),
-		Day:   t.Day(),
-	}
-}
-
 var titleCleanRegexp = regexp.MustCompile(`[^a-z ]`)
 
 // NewID generates a (hopefully) unique ID based on the given title.
@@ -43,22 +23,5 @@ type Post struct {
 	Description string
 	Tags        []string
 	Series      string
-
-	PublishedAt   Date
-	LastUpdatedAt Date
-
-	Body string
-}
-
-// URL returns the relative URL of the Post.
-func (p Post) URL() string {
-	return path.Join(
-		fmt.Sprintf(
-			"%d/%0d/%0d",
-			p.PublishedAt.Year,
-			p.PublishedAt.Month,
-			p.PublishedAt.Day,
-		),
-		p.ID+".html",
-	)
+	Body        string
 }
diff --git a/srv/src/post/store.go b/srv/src/post/store.go
index 235520f..2898315 100644
--- a/srv/src/post/store.go
+++ b/srv/src/post/store.go
@@ -1 +1,404 @@
 package post
+
+import (
+	"database/sql"
+	"errors"
+	"fmt"
+	"path"
+	"strings"
+
+	_ "github.com/mattn/go-sqlite3"
+	migrate "github.com/rubenv/sql-migrate"
+	"github.com/tilinna/clock"
+)
+
+var (
+	// ErrNotFound is used to indicate a Post could not be found in the
+	// database.
+	ErrNotFound = errors.New("not found")
+)
+
+// StoredPost is a Post which has been stored in a Store, and has been given
+// some extra fields as a result.
+type StoredPost struct {
+	Post
+
+	PublishedAt   Date
+	LastUpdatedAt Date
+}
+
+// URL returns the relative URL of the StoredPost.
+func (p StoredPost) URL() string {
+	return path.Join(
+		fmt.Sprintf(
+			"%d/%0d/%0d",
+			p.PublishedAt.Year,
+			p.PublishedAt.Month,
+			p.PublishedAt.Day,
+		),
+		p.ID+".html",
+	)
+}
+
+// Store is used for storing posts to a persistent storage.
+type Store interface {
+
+	// Set sets the Post data into the storage, keyed by the Post's ID. It
+	// overwrites a previous Post with the same ID, if there was one.
+	Set(Post) error
+
+	// Get returns count StoredPosts, sorted time descending, offset by the given page
+	// number. The returned boolean indicates if there are more pages or not.
+	Get(page, count int) ([]StoredPost, bool, error)
+
+	// GetByID will return the StoredPost with the given ID, or ErrNotFound.
+	GetByID(id string) (StoredPost, error)
+
+	// GetBySeries returns all StoredPosts with the given series, sorted time
+	// ascending, or empty slice.
+	GetBySeries(series string) ([]StoredPost, error)
+
+	// GetByTag returns all StoredPosts with the given tag, sorted time
+	// ascending, or empty slice.
+	GetByTag(tag string) ([]StoredPost, error)
+
+	// Delete will delete the StoredPost with the given ID.
+	Delete(id string) error
+
+	Close() error
+}
+
+var migrations = []*migrate.Migration{
+	&migrate.Migration{
+		Id: "1",
+		Up: []string{
+			`CREATE TABLE posts (
+				id          TEXT NOT NULL PRIMARY KEY,
+				title       TEXT NOT NULL,
+				description TEXT NOT NULL,
+				series      TEXT,
+
+				published_at    INTEGER NOT NULL,
+				last_updated_at INTEGER,
+
+				body TEXT NOT NULL
+			)`,
+			`CREATE TABLE post_tags (
+				post_id TEXT NOT NULL,
+				tag     TEXT NOT NULL,
+				UNIQUE(post_id, tag)
+			)`,
+		},
+		Down: []string{
+			"DROP TABLE post_tags",
+			"DROP TABLE posts",
+		},
+	},
+}
+
+// Params are parameters used to initialize a new Store. All fields are required
+// unless otherwise noted.
+type StoreParams struct {
+
+	// Path to the file the database will be stored at.
+	DBFilePath string
+
+	Clock clock.Clock
+}
+
+type store struct {
+	params StoreParams
+	db     *sql.DB
+}
+
+// NewStore initializes a new Store using a sqlite3 database at the given file
+// path.
+func NewStore(params StoreParams) (Store, error) {
+
+	db, err := sql.Open("sqlite3", params.DBFilePath)
+	if err != nil {
+		return nil, fmt.Errorf("opening sqlite file: %w", err)
+	}
+
+	migrations := &migrate.MemoryMigrationSource{Migrations: migrations}
+
+	if _, err := migrate.Exec(db, "sqlite3", migrations, migrate.Up); err != nil {
+		return nil, fmt.Errorf("running migrations: %w", err)
+	}
+
+	return &store{
+		params: params,
+		db:     db,
+	}, nil
+}
+
+func (s *store) Close() error {
+	return s.db.Close()
+}
+
+// if the callback returns an error then the transaction is aborted
+func (s *store) withTx(cb func(*sql.Tx) error) error {
+
+	tx, err := s.db.Begin()
+
+	if err != nil {
+		return fmt.Errorf("starting transaction: %w", err)
+	}
+
+	if err := cb(tx); err != nil {
+
+		if rollbackErr := tx.Rollback(); rollbackErr != nil {
+			return fmt.Errorf(
+				"rolling back transaction: %w (original error: %v)",
+				rollbackErr, err,
+			)
+		}
+
+		return fmt.Errorf("performing transaction: %w (rolled back)", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("committing transaction: %w", err)
+	}
+
+	return nil
+}
+
+func (s *store) Set(post Post) error {
+	return s.withTx(func(tx *sql.Tx) error {
+		currentDate := DateFromTime(s.params.Clock.Now())
+
+		_, err := tx.Exec(
+			`INSERT INTO posts (
+			id, title, description, series, published_at, body
+		)
+		VALUES
+		(?, ?, ?, ?, ?, ?)
+		ON CONFLICT (id) DO UPDATE SET
+			title=excluded.title,
+			description=excluded.description,
+			series=excluded.series,
+			last_updated_at=?,
+			body=excluded.body`,
+			post.ID,
+			post.Title,
+			post.Description,
+			&sql.NullString{String: post.Series, Valid: post.Series != ""},
+			currentDate,
+			post.Body,
+			currentDate,
+		)
+
+		if err != nil {
+			return fmt.Errorf("inserting into posts: %w", err)
+		}
+
+		// this is a bit of a hack, but it allows us to update the tagset without
+		// doing a diff.
+		_, err = tx.Exec(`DELETE FROM post_tags WHERE post_id = ?`, post.ID)
+
+		if err != nil {
+			return fmt.Errorf("clearning post tags: %w", err)
+		}
+
+		for _, tag := range post.Tags {
+
+			_, err = tx.Exec(
+				`INSERT INTO post_tags (post_id, tag) VALUES (?, ?)
+			ON CONFLICT DO NOTHING`,
+				post.ID,
+				tag,
+			)
+
+			if err != nil {
+				return fmt.Errorf("inserting tag %q: %w", tag, err)
+			}
+		}
+
+		return nil
+	})
+}
+
+func (s *store) get(
+	querier interface {
+		Query(string, ...interface{}) (*sql.Rows, error)
+	},
+	limit, offset int,
+	where string, whereArgs ...interface{},
+) (
+	[]StoredPost, error,
+) {
+
+	query := `SELECT
+		p.id, p.title, p.description, p.series, pt.tag,
+		p.published_at, p.last_updated_at,
+		p.body
+	FROM posts p
+	LEFT JOIN post_tags pt ON (p.id = pt.post_id)
+	` + where + `
+	ORDER BY p.published_at ASC, p.title ASC`
+
+	if limit > 0 {
+		query += fmt.Sprintf(" LIMIT %d", limit)
+	}
+
+	if offset > 0 {
+		query += fmt.Sprintf(" OFFSET %d", offset)
+	}
+
+	rows, err := querier.Query(query, whereArgs...)
+
+	if err != nil {
+		return nil, fmt.Errorf("selecting: %w", err)
+	}
+
+	var posts []StoredPost
+
+	for rows.Next() {
+
+		var (
+			post        StoredPost
+			series, tag sql.NullString
+		)
+
+		err := rows.Scan(
+			&post.ID, &post.Title, &post.Description, &series, &tag,
+			&post.PublishedAt, &post.LastUpdatedAt,
+			&post.Body,
+		)
+
+		if err != nil {
+			return nil, fmt.Errorf("scanning row: %w", err)
+		}
+
+		if tag.Valid {
+
+			if l := len(posts); l > 0 && posts[l-1].ID == post.ID {
+				posts[l-1].Tags = append(posts[l-1].Tags, tag.String)
+				continue
+			}
+
+			post.Tags = append(post.Tags, tag.String)
+		}
+
+		post.Series = series.String
+
+		posts = append(posts, post)
+	}
+
+	if err := rows.Close(); err != nil {
+		return nil, fmt.Errorf("closing row iterator: %w", err)
+	}
+
+	return posts, nil
+}
+
+func (s *store) Get(page, count int) ([]StoredPost, bool, error) {
+
+	posts, err := s.get(s.db, count+1, page*count, ``)
+
+	if err != nil {
+		return nil, false, fmt.Errorf("querying posts: %w", err)
+	}
+
+	var hasMore bool
+
+	if len(posts) > count {
+		hasMore = true
+		posts = posts[:count]
+	}
+
+	return posts, hasMore, nil
+}
+
+func (s *store) GetByID(id string) (StoredPost, error) {
+
+	posts, err := s.get(s.db, 0, 0, `WHERE p.id=?`, id)
+
+	if err != nil {
+		return StoredPost{}, fmt.Errorf("querying posts: %w", err)
+	}
+
+	if len(posts) == 0 {
+		return StoredPost{}, ErrNotFound
+	}
+
+	if len(posts) > 1 {
+		panic(fmt.Sprintf("got back multiple posts querying id %q: %+v", id, posts))
+	}
+
+	return posts[0], nil
+}
+
+func (s *store) GetBySeries(series string) ([]StoredPost, error) {
+	return s.get(s.db, 0, 0, `WHERE p.series=?`, series)
+}
+
+func (s *store) GetByTag(tag string) ([]StoredPost, error) {
+
+	var posts []StoredPost
+
+	err := s.withTx(func(tx *sql.Tx) error {
+
+		rows, err := tx.Query(`SELECT post_id FROM post_tags WHERE tag = ?`, tag)
+
+		if err != nil {
+			return fmt.Errorf("querying post_tags by tag: %w", err)
+		}
+
+		var (
+			placeholders []string
+			whereArgs    []interface{}
+		)
+
+		for rows.Next() {
+
+			var id string
+
+			if err := rows.Scan(&id); err != nil {
+				rows.Close()
+				return fmt.Errorf("scanning id: %w", err)
+			}
+
+			whereArgs = append(whereArgs, id)
+			placeholders = append(placeholders, "?")
+		}
+
+		if err := rows.Close(); err != nil {
+			return fmt.Errorf("closing row iterator: %w", err)
+		}
+
+		where := fmt.Sprintf("WHERE p.id IN (%s)", strings.Join(placeholders, ","))
+
+		if posts, err = s.get(tx, 0, 0, where, whereArgs...); err != nil {
+			return fmt.Errorf("querying for ids %+v: %w", whereArgs, err)
+		}
+
+		return nil
+	})
+
+	return posts, err
+}
+
+func (s *store) Delete(id string) error {
+
+	tx, err := s.db.Begin()
+
+	if err != nil {
+		return fmt.Errorf("starting transaction: %w", err)
+	}
+
+	if _, err := tx.Exec(`DELETE FROM post_tags WHERE post_id = ?`, id); err != nil {
+		return fmt.Errorf("deleting from post_tags: %w", err)
+	}
+
+	if _, err := tx.Exec(`DELETE FROM posts WHERE id = ?`, id); err != nil {
+		return fmt.Errorf("deleting from posts: %w", err)
+	}
+
+	if err := tx.Commit(); err != nil {
+		return fmt.Errorf("committing transaction: %w", err)
+	}
+
+	return nil
+}
diff --git a/srv/src/post/store_test.go b/srv/src/post/store_test.go
new file mode 100644
index 0000000..1890511
--- /dev/null
+++ b/srv/src/post/store_test.go
@@ -0,0 +1,248 @@
+package post
+
+import (
+	"io/ioutil"
+	"os"
+	"sort"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/tilinna/clock"
+)
+
+func testPost(i int) Post {
+	istr := strconv.Itoa(i)
+	return Post{
+		ID:          istr,
+		Title:       istr,
+		Description: istr,
+		Body:        istr,
+	}
+}
+
+type storeTestHarness struct {
+	clock *clock.Mock
+	store Store
+}
+
+func newStoreTestHarness(t *testing.T) storeTestHarness {
+
+	clock := clock.NewMock(time.Now().Truncate(1 * time.Hour))
+
+	tmpFile, err := ioutil.TempFile(os.TempDir(), "mediocre-blog-post-store-test-")
+	if err != nil {
+		t.Fatal("Cannot create temporary file", err)
+	}
+	tmpFilePath := tmpFile.Name()
+	tmpFile.Close()
+
+	t.Logf("using temporary sqlite file at %q", tmpFilePath)
+
+	t.Cleanup(func() {
+		if err := os.Remove(tmpFilePath); err != nil {
+			panic(err)
+		}
+	})
+
+	store, err := NewStore(StoreParams{
+		DBFilePath: tmpFilePath,
+		Clock:      clock,
+	})
+	assert.NoError(t, err)
+
+	t.Cleanup(func() {
+		assert.NoError(t, store.Close())
+	})
+
+	return storeTestHarness{
+		clock: clock,
+		store: store,
+	}
+}
+
+func (h *storeTestHarness) testStoredPost(i int) StoredPost {
+	post := testPost(i)
+	return StoredPost{
+		Post:        post,
+		PublishedAt: DateFromTime(h.clock.Now()),
+	}
+}
+
+func TestStore(t *testing.T) {
+
+	assertPostEqual := func(t *testing.T, exp, got StoredPost) {
+		t.Helper()
+		sort.Strings(exp.Tags)
+		sort.Strings(got.Tags)
+		assert.Equal(t, exp, got)
+	}
+
+	assertPostsEqual := func(t *testing.T, exp, got []StoredPost) {
+		t.Helper()
+
+		if !assert.Len(t, got, len(exp), "exp:%+v\ngot: %+v", exp, got) {
+			return
+		}
+
+		for i := range exp {
+			assertPostEqual(t, exp[i], got[i])
+		}
+	}
+
+	t.Run("not_found", func(t *testing.T) {
+		h := newStoreTestHarness(t)
+
+		_, err := h.store.GetByID("foo")
+		assert.ErrorIs(t, err, ErrNotFound)
+	})
+
+	t.Run("set_get_delete", func(t *testing.T) {
+		h := newStoreTestHarness(t)
+
+		nowDate := DateFromTime(h.clock.Now())
+
+		post := testPost(0)
+		post.Tags = []string{"foo", "bar"}
+
+		assert.NoError(t, h.store.Set(post))
+
+		gotPost, err := h.store.GetByID(post.ID)
+		assert.NoError(t, err)
+
+		assertPostEqual(t, StoredPost{
+			Post:        post,
+			PublishedAt: nowDate,
+		}, gotPost)
+
+		// we will now try updating the post on a different day, and ensure it
+		// updates properly
+
+		h.clock.Add(24 * time.Hour)
+		newNowDate := DateFromTime(h.clock.Now())
+
+		post.Title = "something else"
+		post.Series = "whatever"
+		post.Body = "anything"
+		post.Tags = []string{"bar", "baz"}
+
+		assert.NoError(t, h.store.Set(post))
+
+		gotPost, err = h.store.GetByID(post.ID)
+		assert.NoError(t, err)
+
+		assertPostEqual(t, StoredPost{
+			Post:          post,
+			PublishedAt:   nowDate,
+			LastUpdatedAt: newNowDate,
+		}, gotPost)
+
+		// delete the post, it should go away
+		assert.NoError(t, h.store.Delete(post.ID))
+
+		_, err = h.store.GetByID(post.ID)
+		assert.ErrorIs(t, err, ErrNotFound)
+	})
+
+	t.Run("get", func(t *testing.T) {
+		h := newStoreTestHarness(t)
+
+		posts := []StoredPost{
+			h.testStoredPost(0),
+			h.testStoredPost(1),
+			h.testStoredPost(2),
+			h.testStoredPost(3),
+		}
+
+		for _, post := range posts {
+			assert.NoError(t, h.store.Set(post.Post))
+		}
+
+		gotPosts, hasMore, err := h.store.Get(0, 2)
+		assert.NoError(t, err)
+		assert.True(t, hasMore)
+		assertPostsEqual(t, posts[:2], gotPosts)
+
+		gotPosts, hasMore, err = h.store.Get(1, 2)
+		assert.NoError(t, err)
+		assert.False(t, hasMore)
+		assertPostsEqual(t, posts[2:4], gotPosts)
+
+		posts = append(posts, h.testStoredPost(4))
+		assert.NoError(t, h.store.Set(posts[4].Post))
+
+		gotPosts, hasMore, err = h.store.Get(1, 2)
+		assert.NoError(t, err)
+		assert.True(t, hasMore)
+		assertPostsEqual(t, posts[2:4], gotPosts)
+
+		gotPosts, hasMore, err = h.store.Get(2, 2)
+		assert.NoError(t, err)
+		assert.False(t, hasMore)
+		assertPostsEqual(t, posts[4:], gotPosts)
+	})
+
+	t.Run("get_by_series", func(t *testing.T) {
+		h := newStoreTestHarness(t)
+
+		posts := []StoredPost{
+			h.testStoredPost(0),
+			h.testStoredPost(1),
+			h.testStoredPost(2),
+			h.testStoredPost(3),
+		}
+
+		posts[0].Series = "foo"
+		posts[1].Series = "bar"
+		posts[2].Series = "bar"
+
+		for _, post := range posts {
+			assert.NoError(t, h.store.Set(post.Post))
+		}
+
+		fooPosts, err := h.store.GetBySeries("foo")
+		assert.NoError(t, err)
+		assertPostsEqual(t, posts[:1], fooPosts)
+
+		barPosts, err := h.store.GetBySeries("bar")
+		assert.NoError(t, err)
+		assertPostsEqual(t, posts[1:3], barPosts)
+
+		bazPosts, err := h.store.GetBySeries("baz")
+		assert.NoError(t, err)
+		assert.Empty(t, bazPosts)
+	})
+
+	t.Run("get_by_tag", func(t *testing.T) {
+
+		h := newStoreTestHarness(t)
+
+		posts := []StoredPost{
+			h.testStoredPost(0),
+			h.testStoredPost(1),
+			h.testStoredPost(2),
+			h.testStoredPost(3),
+		}
+
+		posts[0].Tags = []string{"foo"}
+		posts[1].Tags = []string{"foo", "bar"}
+		posts[2].Tags = []string{"bar"}
+
+		for _, post := range posts {
+			assert.NoError(t, h.store.Set(post.Post))
+		}
+
+		fooPosts, err := h.store.GetByTag("foo")
+		assert.NoError(t, err)
+		assertPostsEqual(t, posts[:2], fooPosts)
+
+		barPosts, err := h.store.GetByTag("bar")
+		assert.NoError(t, err)
+		assertPostsEqual(t, posts[1:3], barPosts)
+
+		bazPosts, err := h.store.GetByTag("baz")
+		assert.NoError(t, err)
+		assert.Empty(t, bazPosts)
+	})
+}