// Copyright 2019-present Facebook Inc. All rights reserved.
// This source code is licensed under the Apache 2.0 license found
// in the LICENSE file in the root directory of this source tree.

package entsql

import "entgo.io/ent/schema"

// Annotation is a builtin schema annotation for attaching
// SQL metadata to schema objects for both codegen and runtime.
type Annotation struct {
	// The Table option allows overriding the default table
	// name that is generated by ent. For example:
	//
	//	entsql.Annotation{
	//		Table: "Users",
	//	}
	//
	Table string `json:"table,omitempty"`

	// Charset defines the character-set of the table. For example:
	//
	//	entsql.Annotation{
	//		Charset: "utf8mb4",
	//	}
	//
	Charset string `json:"charset,omitempty"`

	// Collation defines the collation of the table (a set of rules for comparing
	// characters in a character set). For example:
	//
	//	entsql.Annotation{
	//		Collation: "utf8mb4_bin",
	//	}
	//
	Collation string `json:"collation,omitempty"`

	// Options defines the additional table options. For example:
	//
	//	entsql.Annotation{
	//		Options: "ENGINE = INNODB",
	//	}
	//
	Options string `json:"options,omitempty"`

	// Size defines the column size in the generated schema. For example:
	//
	//	entsql.Annotation{
	//		Size: 128,
	//	}
	//
	Size int64 `json:"size,omitempty"`

	// Incremental defines the autoincremental behavior of a column. For example:
	//
	//  incrementalEnabled := true
	//  entsql.Annotation{
	//      Incremental: &incrementalEnabled,
	//  }
	//
	// By default, this value is nil defaulting to whatever best fits each scenario.
	//
	Incremental *bool `json:"incremental,omitempty"`

	// OnDelete specifies a custom referential action for DELETE operations on parent
	// table that has matching rows in the child table.
	//
	// For example, in order to delete rows from the parent table and automatically delete
	// their matching rows in the child table, pass the following annotation:
	//
	//	entsql.Annotation{
	//		OnDelete: entsql.Cascade,
	//	}
	//
	OnDelete ReferenceOption `json:"on_delete,omitempty"`
}

// Name describes the annotation name.
func (Annotation) Name() string {
	return "EntSQL"
}

// Merge implements the schema.Merger interface.
func (a Annotation) Merge(other schema.Annotation) schema.Annotation {
	var ant Annotation
	switch other := other.(type) {
	case Annotation:
		ant = other
	case *Annotation:
		if other != nil {
			ant = *other
		}
	default:
		return a
	}
	if t := ant.Table; t != "" {
		a.Table = t
	}
	if c := ant.Charset; c != "" {
		a.Charset = c
	}
	if c := ant.Collation; c != "" {
		a.Collation = c
	}
	if o := ant.Options; o != "" {
		a.Options = o
	}
	if s := ant.Size; s != 0 {
		a.Size = s
	}
	if s := ant.Incremental; s != nil {
		a.Incremental = s
	}
	if s := ant.OnDelete; s != "" {
		a.OnDelete = s
	}
	return a
}

var (
	_ schema.Annotation = (*Annotation)(nil)
	_ schema.Merger     = (*Annotation)(nil)
)

// ReferenceOption for constraint actions.
type ReferenceOption string

// Reference options (actions) specified by ON UPDATE and ON DELETE
// subclauses of the FOREIGN KEY clause.
const (
	NoAction   ReferenceOption = "NO ACTION"
	Restrict   ReferenceOption = "RESTRICT"
	Cascade    ReferenceOption = "CASCADE"
	SetNull    ReferenceOption = "SET NULL"
	SetDefault ReferenceOption = "SET DEFAULT"
)