refactor(backend/models): use pgtype for nullable fields

`sortToSQL` and unimplemented `filterToSQL`

backend/db/db.go

@@ -30,13 +30,14 @@ func InitDB(connString string) error {
 	return nil
 }
 
-func transaction(ctx context.Context, handler func(pgx.Tx) (statusCode int, err error)) (statusCode int, err error) {
+func transaction(handler func(context.Context, pgx.Tx) (statusCode int, err error)) (statusCode int, err error) {
+	ctx := context.Background()
 	tx, err := connPool.Begin(ctx)
 	if err != nil {
 		statusCode = http.StatusInternalServerError
 		return
 	}
-	statusCode, err = handler(tx)
+	statusCode, err = handler(ctx, tx)
 	if err != nil {
 		tx.Rollback(ctx)
 		return

backend/db/utils.go

@@ -0,0 +1,53 @@
+package db
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// Convert "filter" URL param to SQL "WHERE" condition
+func filterToSQL(filter string) (sql string, statusCode int, err error) {
+	// filterTokens := strings.Split(string(filter), ";")
+	sql = "(true)"
+	return
+}
+
+// Convert "sort" URL param to SQL "ORDER BY"
+func sortToSQL(sort string) (sql string, statusCode int, err error) {
+	if sort == "" {
+		return
+	}
+	sortOptions := strings.Split(sort, ",")
+	sql = " ORDER BY "
+	for i, sortOption := range sortOptions {
+		sortOrder := sortOption[:1]
+		sortColumn := sortOption[1:]
+		// parse sorting order marker
+		switch sortOrder {
+		case "+":
+			sortOrder = "ASC"
+		case "-":
+			sortOrder = "DESC"
+		default:
+			err = fmt.Errorf("invalid sorting order mark: %q", sortOrder)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// validate sorting column
+		var n int
+		n, err = strconv.Atoi(sortColumn)
+		if err != nil || n < 0 {
+			err = fmt.Errorf("invalid sorting column: %q", sortColumn)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// add sorting option to query
+		if i > 0 {
+			sql += ","
+		}
+		sql += fmt.Sprintf("%s %s NULLS LAST", sortColumn, sortOrder)
+	}
+	return
+}

backend/models/models.go

@@ -1,6 +1,10 @@
 package models
 
-import "time"
+import (
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
 
 type User struct {
 	Name    string `json:"name"`
@@ -13,28 +17,28 @@ type MIME struct {
 }
 
 type Category struct {
-	ID        string    `json:"id"`
+	ID        string      `json:"id"`
-	Name      string    `json:"name"`
+	Name      string      `json:"name"`
-	Color     string    `json:"color"`
+	Color     pgtype.Text `json:"color"`
-	CreatedAt time.Time `json:"created_at"`
+	CreatedAt time.Time   `json:"created_at"`
-	Creator   User      `json:"creator"`
+	Creator   User        `json:"creator"`
 }
 
 type File struct {
-	ID        string    `json:"id"`
+	ID        string      `json:"id"`
-	Name      string    `json:"name"`
+	Name      pgtype.Text `json:"name"`
-	MIME      MIME      `json:"mime"`
+	MIME      MIME        `json:"mime"`
-	CreatedAt time.Time `json:"created_at"`
+	CreatedAt time.Time   `json:"created_at"`
-	Creator   User      `json:"creator"`
+	Creator   User        `json:"creator"`
 }
 
 type Tag struct {
-	ID        string    `json:"id"`
+	ID        string      `json:"id"`
-	Name      string    `json:"name"`
+	Name      string      `json:"name"`
-	Color     string    `json:"color"`
+	Color     pgtype.Text `json:"color"`
-	Category  Category  `json:"category"`
+	Category  Category    `json:"category"`
-	CreatedAt time.Time `json:"created_at"`
+	CreatedAt time.Time   `json:"created_at"`
-	Creator   User      `json:"creator"`
+	Creator   User        `json:"creator"`
 }
 
 type Autotag struct {