Move schema parsing to its own package

pkg/schema/parse.go

@@ -0,0 +1,64 @@
+package schema
+
+import (
+	"gas_stack/pkg/textutils"
+	"strings"
+
+	"github.com/jinzhu/inflection"
+	"github.com/jmoiron/sqlx"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// InitDB creates an in-memory DB from a given schema string.
+func InitDB(sql_schema string) *sqlx.DB {
+	db := sqlx.MustOpen("sqlite3", ":memory:")
+	db.MustExec(sql_schema)
+	db.MustExec(`
+		create temporary view tables as
+		    select l.schema, l.name, l.type, l.ncol, l.wr, l.strict
+		      from sqlite_schema s
+		 left join pragma_table_list l on s.name = l.name
+		     where s.type = 'table';
+
+		create temporary view columns as
+		    select tables.name as table_name,
+		           table_info.name as column_name,
+		           lower(table_info.type) as column_type,
+		           "notnull",
+	               dflt_value is not null as has_default_value,
+		           ifnull(dflt_value, 0) dflt_value,
+		           pk as is_primary_key,
+       	           fk."table" is not null as is_foreign_key,
+		           ifnull(fk."table", '') as fk_target_table,
+		           ifnull(fk."to", '') as fk_target_column
+		      from tables
+		      join pragma_table_info(tables.name) as table_info
+		 left join pragma_foreign_key_list(tables.name) as fk on fk."from" = column_name;
+	`)
+	return db
+}
+
+// SchemaFromDB takes a DB connection, checks its schema metadata tables, and returns a Schema.
+func SchemaFromDB(db *sqlx.DB) Schema {
+	ret := Schema{}
+
+	var tables []Table
+	err := db.Select(&tables, `select name, strict from tables`)
+	if err != nil {
+		panic(err)
+	}
+
+	for _, tbl := range tables {
+		tbl.TypeName = textutils.SnakeToCamel(inflection.Singular(tbl.TableName))
+		tbl.TypeIDName = tbl.TypeName + "ID"
+		tbl.VarName = strings.ToLower(string(tbl.TableName[0]))
+
+		err := db.Select(&tbl.Columns, `select * from columns where table_name = ?`, tbl.TableName)
+		if err != nil {
+			panic(err)
+		}
+		ret[tbl.TableName] = tbl
+	}
+	return ret
+}

pkg/schema/parse_test.go

@@ -0,0 +1,54 @@
+package schema_test
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"gas_stack/pkg/schema"
+)
+
+func TestParseSchema(t *testing.T) {
+	assert := assert.New(t)
+	schema_sql, err := os.ReadFile("../../sample_data/test_schemas/food.sql")
+	require.NoError(t, err)
+
+	db := schema.InitDB(string(schema_sql))
+	schema := schema.SchemaFromDB(db)
+	expected_tbls := []string{"food_types", "foods", "units", "ingredients", "recipes", "iterations", "db_version"}
+	for _, tbl_name := range expected_tbls {
+		_, is_ok := schema[tbl_name]
+		assert.True(is_ok)
+	}
+
+	foods := schema["foods"]
+	assert.Equal(foods.TableName, "foods")
+	assert.Equal(foods.TypeName, "Food")
+	assert.Equal(foods.TypeIDName, "FoodID")
+	assert.Equal(foods.IsStrict, true)
+	assert.Len(foods.Columns, 20)
+	assert.Equal(foods.Columns[0].Name, "rowid")
+	assert.Equal(foods.Columns[0].Type, "integer")
+	assert.Equal(foods.Columns[0].IsNotNull, false) // Explicit not-null
+	assert.Equal(foods.Columns[0].IsPrimaryKey, true)
+	assert.Equal(foods.Columns[0].IsForeignKey, false)
+	assert.Equal(foods.Columns[1].Name, "name")
+	assert.Equal(foods.Columns[1].Type, "text")
+	assert.Equal(foods.Columns[1].IsNotNull, true)
+	assert.Equal(foods.Columns[1].HasDefaultValue, false)
+	assert.Equal(foods.Columns[1].IsPrimaryKey, false)
+	assert.Equal(foods.Columns[16].Name, "mass")
+	assert.Equal(foods.Columns[16].Type, "real")
+	assert.Equal(foods.Columns[16].HasDefaultValue, true)
+	assert.Equal(foods.Columns[16].DefaultValue, "100")
+
+	ingredients := schema["ingredients"]
+	assert.Equal(ingredients.Columns[0].Name, "rowid")
+	assert.Equal(ingredients.Columns[0].IsPrimaryKey, true)
+	assert.Equal(ingredients.Columns[1].Name, "food_id")
+	assert.Equal(ingredients.Columns[1].IsForeignKey, true)
+	assert.Equal(ingredients.Columns[1].ForeignKeyTargetTable, "foods")
+	assert.Equal(ingredients.Columns[1].ForeignKeyTargetColumn, "rowid")
+}

pkg/schema/table.go

@@ -0,0 +1,34 @@
+package schema
+
+// Column represents a single column in a table.
+type Column struct {
+	TableName              string `db:"table_name"`
+	Name                   string `db:"column_name"`
+	Type                   string `db:"column_type"`
+	IsNotNull              bool   `db:"notnull"`
+	HasDefaultValue        bool   `db:"has_default_value"`
+	DefaultValue           string `db:"dflt_value"`
+	IsPrimaryKey           bool   `db:"is_primary_key"`
+	IsForeignKey           bool   `db:"is_foreign_key"`
+	ForeignKeyTargetTable  string `db:"fk_target_table"`
+	ForeignKeyTargetColumn string `db:"fk_target_column"`
+}
+
+// IsNullableForeignKey is a helper function.
+func (c Column) IsNullableForeignKey() bool {
+	return !c.IsNotNull && !c.IsPrimaryKey && c.IsForeignKey
+}
+
+// Table is a single SQLite table.
+type Table struct {
+	TableName string `db:"name"`
+	IsStrict  bool   `db:"strict"`
+	Columns   []Column
+
+	TypeIDName string
+	VarName    string
+	TypeName   string
+}
+
+// Schema is a container for a bunch of Tables, indexed by table name.
+type Schema map[string]Table