import * as AST from "@effect/schema/AST"
import * as Schema from "@effect/schema/Schema"
import * as ParseResult from "@effect/schema/ParseResult"
import { dual } from "effect/Function"
import * as Data from "effect/Data"

/**
 * @since 1.0.0
 * @category type ids
 */
export const TypeId: unique symbol = Symbol.for("@effect/schema/VariantSchema")

/**
 * @since 1.0.0
 * @category type ids
 */
export type TypeId = typeof TypeId

/**
 * @since 1.0.0
 * @category models
 */
export interface Struct<in out A extends Field.Fields> {
  readonly [TypeId]: A
}

/**
 * @since 1.0.0
 * @category models
 */
export declare namespace Struct {
  /**
   * @since 1.0.0
   * @category models
   */
  export type Fields = {
    readonly [key: string]:
      | Schema.Schema.All
      | Schema.PropertySignature.All
      | Field<any>
      | Struct<any>
  }

  /**
   * @since 1.0.0
   * @category models
   */
  export type FieldsWithKeys<K extends string> = {
    readonly [key: string]:
      | Schema.Schema.All
      | Schema.PropertySignature.All
      | Field<Field.ConfigWithKeys<K>>
      | Struct<FieldsWithKeys<K>>
  }
}

/**
 * @since 1.0.0
 * @category type ids
 */
export const FieldTypeId: unique symbol = Symbol.for(
  "@effect/schema/VariantSchema/Field",
)

/**
 * @since 1.0.0
 * @category type ids
 */
export type FieldTypeId = typeof FieldTypeId

/**
 * @since 1.0.0
 * @category models
 */
export interface Field<in out A extends Field.Config> {
  readonly [FieldTypeId]: FieldTypeId
  readonly schemas: A
}

/**
 * @since 1.0.0
 * @category models
 */
export declare namespace Field {
  /**
   * @since 1.0.0
   * @category models
   */
  export type Config = Partial<{
    readonly [key: string]: Schema.Schema.All | Schema.PropertySignature.All
  }>

  /**
   * @since 1.0.0
   * @category models
   */
  export type ConfigWithKeys<K extends string> = {
    readonly [P in K]?: Schema.Schema.All | Schema.PropertySignature.All
  }

  /**
   * @since 1.0.0
   * @category models
   */
  export type Fields = {
    readonly [key: string]:
      | Schema.Schema.All
      | Schema.PropertySignature.All
      | Field<any>
      | Struct<any>
  }
}

/**
 * @since 1.0.0
 * @category constructors
 */
export const Struct = <const A extends Field.Fields>(fields: A): Struct<A> => ({
  [TypeId]: fields,
})

/**
 * @since 1.0.0
 * @category constructors
 */
export const Field = <const A extends Field.Config>(schemas: A): Field<A> => ({
  [FieldTypeId]: FieldTypeId,
  schemas,
})

/**
 * @since 1.0.0
 * @category extractors
 */
export type ExtractFields<V extends string, Fields extends Struct.Fields> = {
  readonly [K in keyof Fields as [Fields[K]] extends [Field<infer Config>]
    ? V extends keyof Config
      ? K
      : never
    : K]: [Fields[K]] extends [Struct<infer _>]
    ? Extract<V, Fields[K]>
    : [Fields[K]] extends [Field<infer Config>]
      ? [Config[V]] extends [Schema.Schema.All | Schema.PropertySignature.All]
        ? Config[V]
        : never
      : [Fields[K]] extends [Schema.Schema.All | Schema.PropertySignature.All]
        ? Fields[K]
        : never
}

/**
 * @since 1.0.0
 * @category extractors
 */
export type Extract<V extends string, A extends Struct<any>> = [A] extends [
  Struct<infer Fields>,
]
  ? Schema.Struct<Schema.Simplify<ExtractFields<V, Fields>>>
  : never

/**
 * @since 1.0.0
 * @category extractors
 */
export const extract: {
  <V extends string>(
    variant: V,
  ): <A extends Struct<any>>(self: A) => Extract<V, A>
  <V extends string, A extends Struct<any>>(self: A, variant: V): Extract<V, A>
} = dual(
  2,
  <V extends string, A extends Struct<any>>(
    self: A,
    variant: V,
  ): Extract<V, A> => {
    const fields: Record<string, any> = {}
    for (const key of Object.keys(self[TypeId])) {
      const value = self[TypeId][key]
      if (Schema.TypeId in value) {
        fields[key] = value
      } else if (FieldTypeId in value) {
        if (variant in value.schemas) {
          fields[key] = value.schemas[variant]
        }
      } else {
        fields[key] = extract(value, variant)
      }
    }
    return Schema.Struct(fields) as any
  },
)

type RequiredKeys<T> = {
  [K in keyof T]-?: {} extends Pick<T, K> ? never : K
}[keyof T]

/**
 * @category models
 * @since 1.0.0
 */
export interface Class<
  Self,
  Fields extends Struct.Fields,
  SchemaFields extends Schema.Struct.Fields,
  A,
  I,
  R,
  C,
> extends Schema.Schema<Self, Schema.Simplify<I>, R>,
    Struct<Fields> {
  new (
    props: RequiredKeys<C> extends never
      ? void | Schema.Simplify<C>
      : Schema.Simplify<C>,
    options?: {
      readonly disableValidation?: boolean
    },
  ): A

  readonly ast: AST.Transformation

  make<Args extends Array<any>, X>(
    this: { new (...args: Args): X },
    ...args: Args
  ): X

  annotations(
    annotations: Schema.Annotations.Schema<Self>,
  ): Schema.SchemaClass<Self, Schema.Simplify<I>, R>

  readonly identifier: string
  readonly fields: SchemaFields
}

type ClassFromFields<
  Self,
  Fields extends Struct.Fields,
  SchemaFields extends Schema.Struct.Fields,
> = Class<
  Self,
  Fields,
  SchemaFields,
  Schema.Struct.Type<SchemaFields>,
  Schema.Struct.Encoded<SchemaFields>,
  Schema.Struct.Context<SchemaFields>,
  Schema.Struct.Constructor<SchemaFields>
>

type MissingSelfGeneric<Params extends string = ""> =
  `Missing \`Self\` generic - use \`class Self extends Class<Self>()(${Params}{ ... })\``

const schemaVariance = {
  /* c8 ignore next */
  _A: (_: any) => _,
  /* c8 ignore next */
  _I: (_: any) => _,
  /* c8 ignore next */
  _R: (_: never) => _,
}

/**
 * @since 1.0.0
 * @category constructors
 */
export const factory = <
  const Variants extends ReadonlyArray<string>,
  const Default extends Variants[number],
>(options: {
  readonly variants: Variants
  readonly defaultVariant: Default
}): {
  readonly Struct: <const A extends Struct.FieldsWithKeys<Variants[number]>>(
    fields: A,
  ) => Struct<A>
  readonly Field: <const A extends Field.ConfigWithKeys<Variants[number]>>(
    config: A & { readonly [K in Exclude<keyof A, Variants[number]>]: never },
  ) => Field<A>
  readonly Class: <Self = never>(
    identifier: string,
  ) => <Fields extends Struct.Fields>(
    fields: Fields,
    annotations?: Schema.Annotations.Schema<Self>,
  ) => [Self] extends [never]
    ? MissingSelfGeneric
    : ClassFromFields<
        Self,
        Fields,
        Schema.Simplify<ExtractFields<Default, Fields>>
      > & {
        readonly [V in Variants[number]]: Extract<V, Struct<Fields>>
      }
} => {
  function Class<Self>(identifier: string) {
    return function (
      fields: Struct.Fields,
      annotations?: Schema.Annotations.Schema<Self>,
    ) {
      const variantStruct = Struct(fields)
      const schema = extract(variantStruct, options.defaultVariant)
      const validate = ParseResult.validateSync(schema)
      const klass = Schema.Class<any>(identifier)(schema.fields, annotations)
      class Base extends Data.Class {
        constructor(
          props: any,
          options?: { readonly disableValidation?: boolean },
        ) {
          if (options?.disableValidation !== true) {
            props = validate(props)
          }
          super(props)
        }

        // implement Struct
        static [TypeId] = fields

        // implement Schema
        static [Schema.TypeId] = schemaVariance
        static ast = klass.ast
        static make = klass.make
        static fields = klass.fields
        static identifier = klass.identifier
      }
      for (const variant of options.variants) {
        Object.defineProperty(Base, variant, {
          value: extract(variantStruct, variant),
        })
      }
      return Base
    }
  }
  return {
    Struct,
    Field,
    Class,
  } as any
}