Separate exec types into files, document code (#10)

Reviewed-on: #10

exec/count.go

@@ -0,0 +1,96 @@
+package exec
+
+import (
+	"database/sql"
+	"errors"
+	"reflect"
+
+	"git.gdulai.com/gdulai/simpleorm"
+	"git.gdulai.com/gdulai/simpleorm/schema"
+	log "gitlab.com/gdulai/simpleloglvl"
+)
+
+// Count represents a count query.
+type Count[T any] struct {
+	target    schema.Table
+	whereStmt string
+	args      []any
+	result    int64
+}
+
+// CreateCount returns a new instance of Count.
+//
+// orm is the simpleorm.ORM instance which connects, caches and manages the relations.
+func CreateCount[T any](orm *simpleorm.ORM, whereStmt string, args ...any) (Count[T], error) {
+	table, ok := orm.Cache().Get(reflect.TypeFor[T]().Name())
+	if !ok {
+		return Count[T]{}, errors.New("Failed to get table from schema cache")
+	}
+
+	return Count[T]{target: *table, whereStmt: whereStmt, args: args}, nil
+}
+
+// Result returns the result of the count query.
+func (c *Count[T]) Result() int64 {
+	return c.result
+}
+
+// Execute executes the parsed count query against a connection and returns an error if there was any during the execution.
+//
+// conn is the simpleorm.DBConnection which handles the database connection.
+func (c *Count[T]) Execute(conn *simpleorm.DBConnection) error {
+	return c.execute(conn, nil)
+}
+
+// execute executes the parsed count query against a connection and transaction and returns an error if there was any during the execution.
+//
+// conn is the simpleorm.DBConnection which handles the database connection.
+// tx is the sql.Tx transaction which the count query will be run in.
+func (c *Count[T]) execute(conn *simpleorm.DBConnection, tx *sql.Tx) error {
+	// Reinit the results, new execution
+	c.result = -1
+	dml := c.target.GetCountDML()
+
+	if c.whereStmt != "" {
+		dml += " WHERE " + c.whereStmt
+	}
+
+	log.LogDebug("Preparing sql: %s, with args: %s", dml, c.args)
+
+	var stmt *sql.Stmt
+	var err error
+	if tx != nil {
+		stmt, err = tx.Prepare(dml)
+	} else {
+		stmt, err = conn.Prepare(dml)
+	}
+
+	if err != nil {
+		return err
+	}
+	defer stmt.Close()
+
+	log.LogDebug("Executing statement: %s", stmt)
+
+	if len(c.args) == 0 {
+		err = stmt.QueryRow().Scan(&c.result)
+	} else {
+		// Flattent args to make sure it can be parsed correctly
+		var flatArgs []any
+		for _, a := range c.args {
+			if s, ok := a.([]any); ok {
+				flatArgs = append(flatArgs, s...)
+			} else {
+				flatArgs = append(flatArgs, a)
+			}
+		}
+
+		err = stmt.QueryRow(flatArgs...).Scan(&c.result)
+
+	}
+	if err != nil {
+		return err
+	}
+
+	return nil
+}