package gorm

import (
	"database/sql"
	"fmt"
	"go/ast"
	"reflect"
	"regexp"
	"strconv"
	"strings"
	"time"
)

type ModelStruct struct {
	PrimaryKeyField *StructField
	StructFields    []*StructField
	TableName       string
}

type StructField struct {
	DBName       string
	Name         string
	Names        []string
	IsPrimaryKey bool
	IsScanner    bool
	IsTime       bool
	IsNormal     bool
	IsIgnored    bool
	DefaultValue *string
	SqlTag       string
	Tag          reflect.StructTag
	Struct       reflect.StructField
	Relationship *Relationship
}

func (structField *StructField) clone() *StructField {
	return &StructField{
		DBName:       structField.DBName,
		Name:         structField.Name,
		Names:        structField.Names,
		IsPrimaryKey: structField.IsPrimaryKey,
		IsScanner:    structField.IsScanner,
		IsTime:       structField.IsTime,
		IsNormal:     structField.IsNormal,
		IsIgnored:    structField.IsIgnored,
		DefaultValue: structField.DefaultValue,
		SqlTag:       structField.SqlTag,
		Tag:          structField.Tag,
		Struct:       structField.Struct,
		Relationship: structField.Relationship,
	}
}

type Relationship struct {
	Kind                        string
	ForeignType                 string
	ForeignFieldName            string
	ForeignDBName               string
	AssociationForeignFieldName string
	AssociationForeignDBName    string
	JoinTable                   string
}

func (scope *Scope) generateSqlTag(field *StructField) {
	var sqlType string
	reflectValue := reflect.Indirect(reflect.New(field.Struct.Type))
	sqlSettings := parseTagSetting(field.Tag.Get("sql"))

	if value, ok := sqlSettings["TYPE"]; ok {
		sqlType = value
	}

	additionalType := sqlSettings["NOT NULL"] + " " + sqlSettings["UNIQUE"]
	if value, ok := sqlSettings["DEFAULT"]; ok {
		additionalType = additionalType + "DEFAULT " + value
	}

	if field.IsScanner {
		var getScannerValue func(reflect.Value)
		getScannerValue = func(value reflect.Value) {
			reflectValue = value
			if _, isScanner := reflect.New(reflectValue.Type()).Interface().(sql.Scanner); isScanner && reflectValue.Kind() == reflect.Struct {
				getScannerValue(reflectValue.Field(0))
			}
		}
		getScannerValue(reflectValue)
	}

	if sqlType == "" {
		var size = 255

		if value, ok := sqlSettings["SIZE"]; ok {
			size, _ = strconv.Atoi(value)
		}

		if field.IsPrimaryKey {
			sqlType = scope.Dialect().PrimaryKeyTag(reflectValue, size)
		} else {
			sqlType = scope.Dialect().SqlTag(reflectValue, size)
		}
	}

	if strings.TrimSpace(additionalType) == "" {
		field.SqlTag = sqlType
	} else {
		field.SqlTag = fmt.Sprintf("%v %v", sqlType, additionalType)
	}
}

var pluralMapKeys = []*regexp.Regexp{regexp.MustCompile("ch$"), regexp.MustCompile("ss$"), regexp.MustCompile("sh$"), regexp.MustCompile("day$"), regexp.MustCompile("y$"), regexp.MustCompile("x$"), regexp.MustCompile("([^s])s?$")}
var pluralMapValues = []string{"ches", "sses", "shes", "days", "ies", "xes", "${1}s"}

func (scope *Scope) GetModelStruct() *ModelStruct {
	var modelStruct ModelStruct

	reflectValue := reflect.Indirect(reflect.ValueOf(scope.Value))
	if !reflectValue.IsValid() {
		return &modelStruct
	}

	if reflectValue.Kind() == reflect.Slice {
		reflectValue = reflect.Indirect(reflect.New(reflectValue.Type().Elem()))
	}

	scopeType := reflectValue.Type()
	if scope.db != nil {
		if value, ok := scope.db.parent.ModelStructs[scopeType]; ok {
			return value
		} else {
			scope.db.parent.ModelStructs[scopeType] = &modelStruct
		}
	}

	if scopeType.Kind() == reflect.Ptr {
		scopeType = scopeType.Elem()
	}

	if scopeType.Kind() != reflect.Struct {
		return &modelStruct
	}

	// Set tablename
	if fm := reflect.New(scopeType).MethodByName("TableName"); fm.IsValid() {
		if results := fm.Call([]reflect.Value{}); len(results) > 0 {
			if name, ok := results[0].Interface().(string); ok {
				modelStruct.TableName = name
			}
		}
	} else {
		modelStruct.TableName = ToSnake(scopeType.Name())
		if scope.db == nil || !scope.db.parent.singularTable {
			for index, reg := range pluralMapKeys {
				if reg.MatchString(modelStruct.TableName) {
					modelStruct.TableName = reg.ReplaceAllString(modelStruct.TableName, pluralMapValues[index])
				}
			}
		}
	}

	// Set fields
	for i := 0; i < scopeType.NumField(); i++ {
		if fieldStruct := scopeType.Field(i); ast.IsExported(fieldStruct.Name) {
			field := &StructField{
				Struct: fieldStruct,
				Name:   fieldStruct.Name,
				Names:  []string{fieldStruct.Name},
				Tag:    fieldStruct.Tag,
			}

			if fieldStruct.Tag.Get("sql") == "-" {
				field.IsIgnored = true
			} else {
				sqlSettings := parseTagSetting(field.Tag.Get("sql"))
				gormSettings := parseTagSetting(field.Tag.Get("gorm"))
				if _, ok := gormSettings["PRIMARY_KEY"]; ok {
					field.IsPrimaryKey = true
					modelStruct.PrimaryKeyField = field
				}

				if value, ok := sqlSettings["DEFAULT"]; ok {
					field.DefaultValue = &value
				}

				if value, ok := gormSettings["COLUMN"]; ok {
					field.DBName = value
				} else {
					field.DBName = ToSnake(fieldStruct.Name)
				}

				fieldType, indirectType := fieldStruct.Type, fieldStruct.Type
				if indirectType.Kind() == reflect.Ptr {
					indirectType = indirectType.Elem()
				}

				if _, isScanner := reflect.New(fieldType).Interface().(sql.Scanner); isScanner {
					field.IsScanner, field.IsNormal = true, true
				}

				if _, isTime := reflect.New(indirectType).Interface().(*time.Time); isTime {
					field.IsTime, field.IsNormal = true, true
				}

				many2many := gormSettings["MANY2MANY"]
				foreignKey := SnakeToUpperCamel(gormSettings["FOREIGNKEY"])
				foreignType := SnakeToUpperCamel(gormSettings["FOREIGNTYPE"])
				associationForeignKey := SnakeToUpperCamel(gormSettings["ASSOCIATIONFOREIGNKEY"])
				if polymorphic := SnakeToUpperCamel(gormSettings["POLYMORPHIC"]); polymorphic != "" {
					foreignKey = polymorphic + "Id"
					foreignType = polymorphic + "Type"
				}

				if !field.IsNormal {
					switch indirectType.Kind() {
					case reflect.Slice:
						typ := indirectType.Elem()
						if typ.Kind() == reflect.Ptr {
							typ = typ.Elem()
						}

						if typ.Kind() == reflect.Struct {
							kind := "has_many"

							if foreignKey == "" {
								foreignKey = scopeType.Name() + "Id"
							}

							if associationForeignKey == "" {
								associationForeignKey = typ.Name() + "Id"
							}

							if many2many != "" {
								kind = "many_to_many"
							} else if !reflect.New(typ).Elem().FieldByName(foreignKey).IsValid() {
								foreignKey = ""
							}

							field.Relationship = &Relationship{
								JoinTable:                   many2many,
								ForeignType:                 foreignType,
								ForeignFieldName:            foreignKey,
								AssociationForeignFieldName: associationForeignKey,
								ForeignDBName:               ToSnake(foreignKey),
								AssociationForeignDBName:    ToSnake(associationForeignKey),
								Kind: kind,
							}
						} else {
							field.IsNormal = true
						}
					case reflect.Struct:
						if _, ok := gormSettings["EMBEDDED"]; ok || fieldStruct.Anonymous {
							for _, field := range scope.New(reflect.New(indirectType).Interface()).GetStructFields() {
								field = field.clone()
								field.Names = append([]string{fieldStruct.Name}, field.Names...)
								modelStruct.StructFields = append(modelStruct.StructFields, field)
							}
							break
						} else {
							var belongsToForeignKey, hasOneForeignKey, kind string

							if foreignKey == "" {
								belongsToForeignKey = field.Name + "Id"
								hasOneForeignKey = scopeType.Name() + "Id"
							} else {
								belongsToForeignKey = foreignKey
								hasOneForeignKey = foreignKey
							}

							if _, ok := scopeType.FieldByName(belongsToForeignKey); ok {
								kind = "belongs_to"
								foreignKey = belongsToForeignKey
							} else {
								foreignKey = hasOneForeignKey
								kind = "has_one"
							}

							field.Relationship = &Relationship{
								ForeignFieldName: foreignKey,
								ForeignDBName:    ToSnake(foreignKey),
								ForeignType:      foreignType,
								Kind:             kind,
							}
						}

					default:
						field.IsNormal = true
					}
				}
			}
			modelStruct.StructFields = append(modelStruct.StructFields, field)
		}
	}

	for _, field := range modelStruct.StructFields {
		if field.IsNormal {
			if modelStruct.PrimaryKeyField == nil && field.DBName == "id" {
				field.IsPrimaryKey = true
				modelStruct.PrimaryKeyField = field
			}

			if scope.db != nil {
				scope.generateSqlTag(field)
			}
		}
	}

	return &modelStruct
}

func (scope *Scope) GetStructFields() (fields []*StructField) {
	return scope.GetModelStruct().StructFields
}