import {Collection} from '../../util'
import {FieldType} from '../types'

/** The reflection metadata key containing information about the model's fields. */
export const EXTOLLO_ORM_MODEL_FIELDS_METADATA_KEY = 'extollo:orm:Field.ts'

/**
 * Abstract representation of a field on a model.
 */
export interface ModelField {
    databaseKey: string,
    modelKey: string | symbol,
    type: any,
}

/**
 * Retrieve a collection of ModelField metadata from the given model.
 * @param model
 */
export function getFieldsMeta(model: unknown): Collection<ModelField> {
    const fields = Reflect.getMetadata(EXTOLLO_ORM_MODEL_FIELDS_METADATA_KEY, (model as any).constructor)
    if ( !(fields instanceof Collection) ) {
        return new Collection<ModelField>()
    }

    return fields as Collection<ModelField>
}

/**
 * Set the collection of ModelField metadata as the field data for the given model.
 * @param model
 * @param fields
 */
export function setFieldsMeta(model: unknown, fields: Collection<ModelField>): void {
    Reflect.defineMetadata(EXTOLLO_ORM_MODEL_FIELDS_METADATA_KEY, fields, (model as any).constructor)
}

/**
 * Decorator that maps the given property to a database column of the specified FieldType.
 *
 * @example
 * ```typescript
 * class MyModel extends Model<MyModel> {
 *     // Maps the 'name' VARCHAR column in the database to this property
 *     @Field(FieldType.Varchar)
 *     public name!: string
 *
 *     // Maps the 'first_name' VARCHAR column in the database to this property
 *     @Field(FieldType.Varchar, 'first_name')
 *     public firstName!: string
 * }
 * ```
 *
 * @param type
 * @param databaseKey
 * @constructor
 */
export function Field(type: FieldType, databaseKey?: string): PropertyDecorator {
    return (target, modelKey) => {
        if ( !databaseKey ) {
            databaseKey = String(modelKey)
        }
        const fields = getFieldsMeta(target)

        const existingField = fields.firstWhere('modelKey', '=', modelKey)
        if ( existingField ) {
            existingField.databaseKey = databaseKey
            existingField.type = type
            return setFieldsMeta(target, fields)
        }

        fields.push({
            databaseKey,
            modelKey,
            type,
        })

        setFieldsMeta(target, fields)
    }
}