gormcol/gormcol.go

package gormcol

import (
	"fmt"
	"reflect"
	"strings"

	"gorm.io/gorm/schema"
)

// NamingStrategy is the GORM naming strategy used for column/table name resolution.
// Defaults to gorm.io/gorm/schema.NamingStrategy.
// Set this to NamingStrategy when using within a project that has a database connection.
var NamingStrategy schema.Namer = schema.NamingStrategy{}

type Tabler interface {
	TableName() string
}

// Field represents a GORM column descriptor with table context.
// Define package-level variables to get type-safe column references:
//
//	var PsAccess = struct {
//	    IDProfile           gormcol.Field
//	    IDAuthorizationRole gormcol.Field
//	}{
//	    IDProfile:           gormcol.Field{Table: "ps_access", Column: "id_profile"},
//	    IDAuthorizationRole: gormcol.Field{Table: "ps_access", Column: "id_authorization_role"},
//	}
type Field struct {
	Table  string
	Column string
}

// Column returns the column name from a Field descriptor.
//
//	gormcol.Column(prestadb.PsAccess.IDAuthorizationRole) // "id_authorization_role"
func Column(f Field) string {
	return f.Column
}

// ColumnOnTable returns "table.column" from a Field descriptor.
//
//	gormcol.ColumnOnTable(prestadb.PsAccess.IDAuthorizationRole) // "ps_access.id_authorization_role"
func ColumnOnTable(f Field) string {
	return f.Table + "." + f.Column
}

// TableField returns the table name from a Field descriptor.
func TableField(f Field) string {
	return f.Table
}

// -- Reflection-based utilities (for structs without Field descriptors) --

// Col extracts the GORM column name from the `gorm:"column:..."` struct tag.
//
//	gormcol.Col[prestadb.PsAccess]("IDAuthorizationRole") // "id_authorization_role"
func Col[T any](fieldName string) string {
	var zero T
	typ := reflect.TypeOf(zero)
	return columnFromType(typ, fieldName)
}

// ColOf extracts a GORM column name from a field on a nested struct referenced
// by structFieldName.
func ColOf[T, S any](structFieldName, fieldName string) string {
	var zero T
	typ := reflect.TypeOf(zero)

	field, ok := typ.FieldByName(structFieldName)
	if !ok {
		panic(fmt.Sprintf("gormcol: struct %q has no field %q", typ.Name(), structFieldName))
	}

	return columnFromType(field.Type, fieldName)
}

// Tbl returns the table name for a GORM model.
// Uses TableName() method if the struct implements Tabler,
// otherwise falls back to the GORM naming strategy.
//
//	gormcol.Tbl[prestadb.PsAccess]() // "ps_access"
func Tbl[T any]() string {
	var zero T
	if t, ok := any(zero).(Tabler); ok {
		return t.TableName()
	}
	typ := reflect.TypeOf(zero)
	return NamingStrategy.TableName(typ.Name())
}

// ColOnTbl returns the column prefixed with the table name (reflection-based).
//
//	gormcol.ColOnTbl[prestadb.PsAccess]("IDAuthorizationRole") // "ps_access.id_authorization_role"
func ColOnTbl[T any](fieldName string) string {
	return Tbl[T]() + "." + Col[T](fieldName)
}

// PK returns the primary key column name for a GORM model.
//
//	gormcol.PK[prestadb.PsAccess]() // "id_authorization_role"
func PK[T any]() string {
	var zero T
	typ := reflect.TypeOf(zero)

	for i := 0; i < typ.NumField(); i++ {
		field := typ.Field(i)
		gormTag := field.Tag.Get("gorm")
		if gormTag == "" || gormTag == "-" {
			continue
		}
		for _, part := range strings.Split(gormTag, ";") {
			if strings.TrimSpace(part) == "primaryKey" {
				return parseGormColumn(gormTag)
			}
		}
	}
	return ""
}

// Columns returns all GORM column names for a struct type.
//
//	gormcol.Columns[prestadb.PsAccess]() // []string{"id_profile", "id_authorization_role"}
func Columns[T any]() []string {
	var zero T
	typ := reflect.TypeOf(zero)

	var cols []string
	for i := 0; i < typ.NumField(); i++ {
		field := typ.Field(i)
		if field.PkgPath != "" {
			continue
		}
		col := parseGormColumn(field.Tag.Get("gorm"))
		if col == "" {
			col = NamingStrategy.ColumnName(typ.Name(), field.Name)
		}
		cols = append(cols, col)
	}
	return cols
}

// ColByJSON finds the GORM column name by matching the struct field's json tag.
//
//	gormcol.ColByJSON[prestadb.PsAccess]("id_authorization_role") // "id_authorization_role"
func ColByJSON[T any](jsonName string) string {
	var zero T
	typ := reflect.TypeOf(zero)

	for i := 0; i < typ.NumField(); i++ {
		field := typ.Field(i)
		jsonTag := field.Tag.Get("json")
		if jsonTag == "" {
			continue
		}
		tagName := strings.Split(jsonTag, ",")[0]
		if tagName == jsonName {
			return columnFromType(typ, field.Name)
		}
	}
	panic(fmt.Sprintf("gormcol: struct %q has no field with json tag %q", typ.Name(), jsonName))
}

func columnFromType(typ reflect.Type, fieldName string) string {
	field, ok := typ.FieldByName(fieldName)
	if !ok {
		panic(fmt.Sprintf("gormcol: struct %q has no field %q", typ.Name(), fieldName))
	}

	gormTag := field.Tag.Get("gorm")
	if gormTag == "" || gormTag == "-" {
		return NamingStrategy.ColumnName(typ.Name(), fieldName)
	}

	col := parseGormColumn(gormTag)
	if col != "" {
		return col
	}

	return NamingStrategy.ColumnName(typ.Name(), fieldName)
}