[ref] refactor adapter, add dialect registry for future extensibility

Signed-off-by: Anton Nesterov <anton@demiurg.io>

pkg/__test__/builder_test.go

@@ -21,7 +21,7 @@ func TestBuilderBasic(t *testing.T) {
 		t.Fatalf("failed to create table: %v", err)
 	}
 
-	insert, values := builder.New(adapter.SQLite{}).In("test t").Insert([]builder.Map{
+	insert, values := builder.New(adapter.CommonDialect{}).In("test t").Insert([]builder.Map{
 		{"name": "a"},
 		{"name": 'b'},
 	}).Sql()
@@ -31,7 +31,7 @@ func TestBuilderBasic(t *testing.T) {
 		t.Fatalf("failed to insert data: %v", err)
 	}
 
-	expr, values := builder.New(adapter.SQLite{}).In("test t").Find(builder.Find{"name": builder.Is{"$in": []interface{}{"a", 98}}}).Sql()
+	expr, values := builder.New(adapter.CommonDialect{}).In("test t").Find(builder.Find{"name": builder.Is{"$in": []interface{}{"a", 98}}}).Sql()
 	fmt.Println(expr)
 	rows, err := a.Query(adapter.Query{
 		Db:         "file::memory:?cache=shared",

pkg/__test__/proto_test.go

@@ -16,7 +16,7 @@ func TestProtoMessagePack(t *testing.T) {
 	}
 	req := proto.Request{}
 	req.UnmarshalMsg(message)
-	query, err := req.Parse(adapter.SQLite{})
+	query, err := req.Parse(adapter.CommonDialect{})
 	if err != nil {
 		t.Fatalf("failed to parse query: %v", err)
 	}

pkg/adapter/CommonDialect.go

@@ -7,13 +7,17 @@ import (
 	utils "l12.xyz/dal/utils"
 )
 
-type SQLite struct {
+/**
+* CommonDialect is a simple implementation of the Dialect interface.
+* Should be usable for most SQL databases.
+**/
+type CommonDialect struct {
 	TableName  string
 	TableAlias string
 	FieldName  string
 }
 
-func (c SQLite) New(opts DialectOpts) Dialect {
+func (c CommonDialect) New(opts DialectOpts) Dialect {
 	tn := opts["TableName"]
 	if tn == "" {
 		tn = c.TableName
@@ -26,18 +30,18 @@ func (c SQLite) New(opts DialectOpts) Dialect {
 	if fn == "" {
 		fn = c.FieldName
 	}
-	return SQLite{
+	return CommonDialect{
 		TableName:  tn,
 		TableAlias: ta,
 		FieldName:  fn,
 	}
 }
 
-func (c SQLite) GetTableName() string {
+func (c CommonDialect) GetTableName() string {
 	return c.TableName
 }
 
-func (c SQLite) GetFieldName() string {
+func (c CommonDialect) GetFieldName() string {
 	if strings.Contains(c.FieldName, ".") {
 		return c.FieldName
 	}
@@ -47,7 +51,7 @@ func (c SQLite) GetFieldName() string {
 	return c.FieldName
 }
 
-func (c SQLite) GetColumnName(key string) string {
+func (c CommonDialect) GetColumnName(key string) string {
 	if strings.Contains(key, ".") {
 		return key
 	}
@@ -57,7 +61,7 @@ func (c SQLite) GetColumnName(key string) string {
 	return key
 }
 
-func (c SQLite) NormalizeValue(value interface{}) interface{} {
+func (c CommonDialect) NormalizeValue(value interface{}) interface{} {
 	str, isStr := value.(string)
 	if !isStr {
 		return value

pkg/adapter/registry.go

@@ -0,0 +1,24 @@
+package adapter
+
+import "fmt"
+
+var DIALECTS = map[string]Dialect{
+	"sqlite3": CommonDialect{},
+}
+
+/**
+ * Register a new dialect for a given driver name.
+ * `driverName` is the valid name of the db driver (e.g. "sqlite3", "postgres").
+ * `dialect` is an implementation of the Dialect interface.
+**/
+func RegisterDialect(driverName string, dialect Dialect) {
+	DIALECTS[driverName] = dialect
+}
+
+func GetDialect(driverName string) Dialect {
+	dialect, ok := DIALECTS[driverName]
+	if !ok {
+		panic(fmt.Errorf("db driver %s not found", driverName))
+	}
+	return dialect
+}

pkg/adapter/types.go

@@ -8,6 +8,9 @@ type Query struct {
 
 type DialectOpts map[string]string
 
+/**
+* Dialect interface provides general utilities for normalizing values for particular DB.
+**/
 type Dialect interface {
 	New(opts DialectOpts) Dialect
 	GetTableName() string
@@ -15,8 +18,3 @@ type Dialect interface {
 	GetColumnName(key string) string
 	NormalizeValue(interface{}) interface{}
 }
-
-var DIALECTS = map[string]Dialect{
-	"sqlite3": SQLite{},
-	"sqlite":  SQLite{},
-}

pkg/builder/Builder_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestBuilderFind(t *testing.T) {
-	db := New(SQLiteContext{})
+	db := New(CommonDialect{})
 	db.In("table t").Find(Query{
 		"field": "value",
 		"a":     1,
@@ -19,7 +19,7 @@ func TestBuilderFind(t *testing.T) {
 }
 
 func TestBuilderFields(t *testing.T) {
-	db := New(SQLiteContext{})
+	db := New(CommonDialect{})
 	db.In("table t")
 	db.Find(Query{
 		"field": "value",
@@ -37,7 +37,7 @@ func TestBuilderFields(t *testing.T) {
 }
 
 func TestBuilderGroup(t *testing.T) {
-	db := New(SQLiteContext{})
+	db := New(CommonDialect{})
 	db.In("table t")
 	db.Find(Query{
 		"field": Is{
@@ -57,7 +57,7 @@ func TestBuilderGroup(t *testing.T) {
 }
 
 func TestBuilderJoin(t *testing.T) {
-	db := New(SQLiteContext{})
+	db := New(CommonDialect{})
 	db.In("table t")
 	db.Find(Query{
 		"field": "value",

pkg/builder/convert_conflict_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestConvertConflict(t *testing.T) {
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableName:  "test",
 		TableAlias: "t",
 		FieldName:  "test",

pkg/builder/convert_find_test.go

@@ -12,7 +12,7 @@ func TestConvertFind(t *testing.T) {
 			"$gt": 2,
 		},
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, values := covertFind(ctx, find)
@@ -39,7 +39,7 @@ func TestConvertFindAnd(t *testing.T) {
 			},
 		},
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, values := covertFind(ctx, find)
@@ -61,7 +61,7 @@ func TestConvertFindOr(t *testing.T) {
 			},
 		},
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, values := covertFind(ctx, find)

pkg/builder/convert_insert_test.go

@@ -6,7 +6,7 @@ import (
 )
 
 func TestConvertInsert(t *testing.T) {
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableName:  "test",
 		TableAlias: "t",
 	}

pkg/builder/convert_join_test.go

@@ -3,12 +3,8 @@ package builder
 import (
 	"fmt"
 	"testing"
-
-	adapter "l12.xyz/dal/adapter"
 )
 
-type SQLiteContext = adapter.SQLite
-
 func TestJoin(t *testing.T) {
 	j := Join{
 		For: "artist a",
@@ -17,7 +13,7 @@ func TestJoin(t *testing.T) {
 		},
 		As: "LEFT",
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, vals := j.Convert(ctx)
@@ -38,7 +34,7 @@ func TestConvertJoin(t *testing.T) {
 			},
 		},
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, vals := convertJoin(ctx, joins...)
@@ -56,7 +52,7 @@ func TestConvertMap(t *testing.T) {
 	joins := []interface{}{
 		Map{"$for": "artist a", "$do": Map{"a.impl": "t.impl"}, "$as": "LEFT"},
 	}
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 	}
 	result, vals := convertJoin(ctx, joins...)

pkg/builder/convert_sort_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestConvertSort(t *testing.T) {
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableAlias: "t",
 		FieldName:  "test",
 	}

pkg/builder/convert_update_test.go

@@ -5,7 +5,7 @@ import (
 )
 
 func TestConvertUpdate(t *testing.T) {
-	ctx := SQLiteContext{
+	ctx := CommonDialect{
 		TableName:  "test",
 		TableAlias: "t",
 		FieldName:  "test",

pkg/builder/types.go

@@ -5,6 +5,7 @@ import (
 	filters "l12.xyz/dal/filters"
 )
 
+type CommonDialect = adapter.CommonDialect
 type Map = map[string]interface{}
 type Fields = Map
 type Find = filters.Find

pkg/server/query_handler.go

@@ -1,7 +1,6 @@
 package server
 
 import (
-	"fmt"
 	"io"
 	"net/http"
 	"reflect"
@@ -10,11 +9,17 @@ import (
 	"l12.xyz/dal/proto"
 )
 
+/**
+* QueryHandler is a http.Handler that reads a proto.Request from the request body,
+* parses it into a query, executes the query on the provided db and writes the
+* result to the response body.
+* - The request body is expected to be in msgpack format (proto.Request).
+* - The response body is written in msgpack format.
+* - The respose is a stream of rows (proto.Row), where the first row is the column names.
+* - The columns are sorted alphabetically, so it is client's responsibility to match them and sort as needed.
+**/
 func QueryHandler(db adapter.DBAdapter) http.Handler {
-	dialect, ok := adapter.DIALECTS[db.Type]
-	if !ok {
-		panic(fmt.Errorf("dialect %s not found", db.Type))
-	}
+	dialect := adapter.GetDialect(db.Type)
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 
 		bodyReader, err := r.GetBody()

pkg/server/query_handler_test.go

@@ -15,6 +15,7 @@ import (
 )
 
 func TestQueryHandler(t *testing.T) {
+	adapter.RegisterDialect("sqlite3", adapter.CommonDialect{})
 	a := adapter.DBAdapter{Type: "sqlite3"}
 	db, err := a.Open("file::memory:?cache=shared")
 	if err != nil {
@@ -52,9 +53,7 @@ func TestQueryHandler(t *testing.T) {
 		t.Fatal(err)
 	}
 	rr := httptest.NewRecorder()
-	handler := QueryHandler(adapter.DBAdapter{
-		Type: "sqlite3",
-	})
+	handler := QueryHandler(a)
 	handler.ServeHTTP(rr, req)
 	res, _ := io.ReadAll(rr.Result().Body)
 	result := proto.UnmarshalRows(res)