opencode/packages/core/src/form.ts

export * as Form from "./form"

import { Form } from "@opencode-ai/schema/form"
import { Cache, Context, Deferred, Duration, Effect, Exit, Layer, Option, Schema } from "effect"
import { makeLocationNode } from "./effect/app-node"
import { EventV2 } from "./event"

const RETENTION = Duration.minutes(10)

export const ID = Form.ID
export type ID = typeof ID.Type

export const Info = Form.Info
export type Info = typeof Info.Type

export const Field = Form.Field
export type Field = Form.Field

export const Fields = Form.Fields
export type Fields = Form.Fields

export const When = Form.When
export type When = Form.When

export const State = Form.State
export type State = typeof State.Type
export type TerminalState = Exclude<State, { readonly status: "pending" }>

export const Answer = Form.Answer
export type Answer = typeof Answer.Type

export const Reply = Form.Reply
export type Reply = typeof Reply.Type

export const Event = Form.Event

export class NotFoundError extends Schema.TaggedErrorClass<NotFoundError>()("Form.NotFoundError", {
  id: ID,
}) {
  override get message() {
    return `Form not found: ${this.id}`
  }
}

export class AlreadySettledError extends Schema.TaggedErrorClass<AlreadySettledError>()("Form.AlreadySettledError", {
  id: ID,
}) {
  override get message() {
    return `Form already settled: ${this.id}`
  }
}

export class AlreadyExistsError extends Schema.TaggedErrorClass<AlreadyExistsError>()("Form.AlreadyExistsError", {
  id: ID,
}) {
  override get message() {
    return `Form already exists: ${this.id}`
  }
}

export class InvalidAnswerError extends Schema.TaggedErrorClass<InvalidAnswerError>()("Form.InvalidAnswerError", {
  id: ID,
  message: Schema.String,
}) {}

export class InvalidFormError extends Schema.TaggedErrorClass<InvalidFormError>()("Form.InvalidFormError", {
  message: Schema.String,
}) {}

export type CreateInput = Omit<Form.Info, "id"> & { readonly id?: ID }

export interface ReplyInput {
  readonly id: ID
  readonly answer: Answer
}

export interface ListInput {
  readonly sessionID?: Form.Info["sessionID"]
}

export interface Interface {
  readonly create: (input: CreateInput) => Effect.Effect<Info, AlreadyExistsError | InvalidFormError>
  readonly ask: (input: CreateInput) => Effect.Effect<TerminalState, AlreadyExistsError | InvalidFormError>
  readonly get: (id: ID) => Effect.Effect<Info, NotFoundError>
  readonly list: (input?: ListInput) => Effect.Effect<ReadonlyArray<Info>>
  readonly state: (id: ID) => Effect.Effect<State, NotFoundError>
  readonly reply: (input: ReplyInput) => Effect.Effect<void, AlreadySettledError | InvalidAnswerError | NotFoundError>
  readonly cancel: (id: ID) => Effect.Effect<void, AlreadySettledError | NotFoundError>
}

export class Service extends Context.Service<Service, Interface>()("@opencode/Form") {}

interface Entry {
  readonly form: Info
  readonly state: State
  readonly deferred: Deferred.Deferred<TerminalState>
}

export const layer = Layer.effect(
  Service,
  Effect.gen(function* () {
    const events = yield* EventV2.Service
    const forms = yield* Cache.makeWith<ID, Entry>(
      () => Effect.die(new Error("Form cache must be used via set/getSuccess, never get")),
      {
        capacity: Number.MAX_SAFE_INTEGER,
        timeToLive: (exit) =>
          Exit.isSuccess(exit) && exit.value.state.status === "pending" ? Duration.infinity : RETENTION,
      },
    )

    const find = Effect.fn("Form.find")(function* (id: ID) {
      return yield* Cache.getSuccess(forms, id).pipe(
        Effect.flatMap((entry) =>
          Option.match(entry, {
            onNone: () => Effect.fail(new NotFoundError({ id })),
            onSome: Effect.succeed,
          }),
        ),
      )
    })

    const create = Effect.fn("Form.create")((input: CreateInput) =>
      Effect.uninterruptible(
        Effect.gen(function* () {
          const id = input.id ?? ID.create()
          const existing = yield* Cache.getSuccess(forms, id)
          if (Option.isSome(existing)) return yield* new AlreadyExistsError({ id })
          const invalid = validateFields(input.fields)
          if (invalid) return yield* new InvalidFormError({ message: invalid })
          const form: Info = {
            id,
            sessionID: input.sessionID,
            title: input.title,
            ...(input.metadata === undefined ? {} : { metadata: input.metadata }),
            fields: input.fields,
          }
          const entry: Entry = {
            form,
            state: { status: "pending" },
            deferred: yield* Deferred.make<TerminalState>(),
          }
          yield* Cache.set(forms, id, entry)
          yield* events.publish(Event.Created, { form }).pipe(Effect.onError(() => Cache.invalidate(forms, id)))
          return form
        }),
      ),
    )

    const ask = Effect.fn("Form.ask")((input: CreateInput) =>
      Effect.uninterruptibleMask((restore) =>
        Effect.gen(function* () {
          const form = yield* create(input)
          const entry = yield* find(form.id).pipe(Effect.orDie)
          return yield* restore(Deferred.await(entry.deferred)).pipe(
            Effect.onInterrupt(() => Effect.ignore(cancel(form.id))),
          )
        }),
      ),
    )

    const get = Effect.fn("Form.get")(function* (id: ID) {
      return (yield* find(id)).form
    })

    const list = Effect.fn("Form.list")(function* (input?: ListInput) {
      const entries = yield* Cache.values(forms)
      return Array.from(entries)
        .filter((entry) => entry.state.status === "pending")
        .filter((entry) => input?.sessionID === undefined || entry.form.sessionID === input.sessionID)
        .map((entry) => entry.form)
    })

    const state = Effect.fn("Form.state")(function* (id: ID) {
      return (yield* find(id)).state
    })

    const reply = Effect.fn("Form.reply")((input: ReplyInput) =>
      Effect.uninterruptible(
        Effect.gen(function* () {
          const entry = yield* find(input.id)
          if (entry.state.status !== "pending") return yield* new AlreadySettledError({ id: input.id })
          const invalid = validateAnswer(entry.form, input.answer)
          if (invalid) return yield* new InvalidAnswerError({ id: input.id, message: invalid })
          const next: TerminalState = { status: "answered", answer: input.answer }
          yield* events.publish(Event.Replied, { id: input.id, sessionID: entry.form.sessionID, answer: input.answer })
          yield* Cache.set(forms, input.id, { ...entry, state: next })
          yield* Deferred.succeed(entry.deferred, next)
        }),
      ),
    )

    const cancel = Effect.fn("Form.cancel")((id: ID) =>
      Effect.uninterruptible(
        Effect.gen(function* () {
          const entry = yield* find(id)
          if (entry.state.status !== "pending") return yield* new AlreadySettledError({ id })
          const next: TerminalState = { status: "cancelled" }
          yield* events.publish(Event.Cancelled, { id, sessionID: entry.form.sessionID })
          yield* Cache.set(forms, id, { ...entry, state: next })
          yield* Deferred.succeed(entry.deferred, next)
        }),
      ),
    )

    yield* Effect.addFinalizer(() =>
      Cache.values(forms).pipe(
        Effect.flatMap((entries) =>
          Effect.forEach(
            Array.from(entries).filter((entry) => entry.state.status === "pending"),
            (entry) => cancel(entry.form.id).pipe(Effect.ignore),
            { discard: true },
          ),
        ),
      ),
    )

    return Service.of({ create, ask, get, list, state, reply, cancel })
  }),
)

export const locationLayer = layer

export const node = makeLocationNode({ service: Service, layer, deps: [EventV2.node] })

function validateAnswer(form: Info, answer: Answer) {
  const fields = new Map(form.fields.map((field) => [field.key, field] as const))
  for (const key of Object.keys(answer)) {
    if (!fields.has(key)) return `Unknown form field: ${key}`
  }
  for (const field of form.fields) {
    const value = answer[field.key]
    if (field.type === "external") {
      if (value !== true) return `External form field must be acknowledged: ${field.key}`
      continue
    }
    const active = isActive(field, answer)
    if (value === undefined) {
      if (field.required && active) return `Missing required form field: ${field.key}`
      continue
    }
    if (!active) return `Form field is not active: ${field.key}`
    const invalid = validateField(field, value)
    if (invalid) return invalid
  }
}

type InputField = Exclude<Form.Field, Form.ExternalField>

function isActive(field: InputField, answer: Answer) {
  if (!field.when) return true
  return field.when.every((when) => matches(when, answer[when.key]))
}

// An unanswered referenced field makes the condition false for both ops. Combined with inactive
// fields being unanswerable, this cascades: hiding a field falsifies every condition referencing it.
function matches(when: Form.When, value: Form.Value | undefined) {
  if (value === undefined) return false
  const hit = Array.isArray(value) ? value.some((item) => item === when.value) : value === when.value
  return when.op === "eq" ? hit : !hit
}

// Create-time validation of `when` references: each condition must point at an earlier field,
// carry a value matching that field's type, and use a declared option when the field's options
// are closed. Rejecting these at creation surfaces authoring mistakes to the caller instead of
// silently never matching.
function validateFields(fields: ReadonlyArray<Form.Field>) {
  if (fields.length === 0) return "Form must have at least one field"
  const earlier = new Map<string, InputField>()
  const keys = new Set<string>()
  for (const field of fields) {
    if (keys.has(field.key)) return `Duplicate form field key: ${field.key}`
    keys.add(field.key)
    if (field.type === "external") continue
    for (const when of field.when ?? []) {
      const target = earlier.get(when.key)
      if (!target) return `Form field condition must reference an earlier field: ${field.key} -> ${when.key}`
      const invalid = validateWhen(when, target)
      if (invalid) return `${invalid}: ${field.key} -> ${when.key}`
    }
    earlier.set(field.key, field)
  }
}

function validateWhen(when: Form.When, target: InputField) {
  if (target.type === "boolean") {
    if (typeof when.value !== "boolean") return "Form field condition value must be a boolean"
    return
  }
  if (target.type === "number" || target.type === "integer") {
    if (typeof when.value !== "number") return "Form field condition value must be a number"
    return
  }
  // string and multiselect targets both compare against string values
  if (typeof when.value !== "string") return "Form field condition value must be a string"
  const closed = target.type === "multiselect" ? !target.custom : target.options !== undefined && !target.custom
  if (closed && !target.options?.some((option) => option.value === when.value)) {
    return "Form field condition value must be one of the field's options"
  }
}

function validateField(field: InputField, value: Form.Value): string | undefined {
  if (field.type === "string") {
    if (typeof value !== "string") return `Expected string for form field: ${field.key}`
    if (field.required && value.length === 0) return `Missing required form field: ${field.key}`
    if (field.minLength !== undefined && value.length < field.minLength) return `Form field is too short: ${field.key}`
    if (field.maxLength !== undefined && value.length > field.maxLength) return `Form field is too long: ${field.key}`
    if (field.pattern !== undefined) {
      try {
        if (!new RegExp(field.pattern).test(value)) return `Form field does not match pattern: ${field.key}`
      } catch {
        return `Form field has invalid pattern: ${field.key}`
      }
    }
    if (field.format === "email" && !/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(value))
      return `Expected email for form field: ${field.key}`
    if (field.format === "uri" && !isUri(value)) return `Expected URI for form field: ${field.key}`
    if (field.format === "date" && !isDate(value)) return `Expected date for form field: ${field.key}`
    if (field.format === "date-time" && !isDateTime(value)) return `Expected date-time for form field: ${field.key}`
    if (field.options && !field.custom && !field.options.some((option) => option.value === value)) {
      return `Invalid option for form field: ${field.key}`
    }
    return
  }
  if (field.type === "number" || field.type === "integer") {
    if (typeof value !== "number" || !Number.isFinite(value)) return `Expected number for form field: ${field.key}`
    if (field.type === "integer" && !Number.isInteger(value)) return `Expected integer for form field: ${field.key}`
    if (field.minimum !== undefined && value < field.minimum) return `Form field is too small: ${field.key}`
    if (field.maximum !== undefined && value > field.maximum) return `Form field is too large: ${field.key}`
    return
  }
  if (field.type === "boolean") {
    if (typeof value !== "boolean") return `Expected boolean for form field: ${field.key}`
    return
  }
  if (field.type === "multiselect") {
    if (!isStringArray(value)) return `Expected string array for form field: ${field.key}`
    if (field.required && value.length === 0) return `Missing required form field: ${field.key}`
    if (field.minItems !== undefined && value.length < field.minItems)
      return `Too few selections for form field: ${field.key}`
    if (field.maxItems !== undefined && value.length > field.maxItems)
      return `Too many selections for form field: ${field.key}`
    if (!field.custom && value.some((item) => !field.options.some((option) => option.value === item))) {
      return `Invalid option for form field: ${field.key}`
    }
  }
}

function isStringArray(value: Form.Value): value is ReadonlyArray<string> {
  return Array.isArray(value) && value.every((item): item is string => typeof item === "string")
}

function isUri(value: string) {
  try {
    new URL(value)
    return true
  } catch {
    return false
  }
}

function isDate(value: string) {
  if (!/^\d{4}-\d{2}-\d{2}$/.test(value)) return false
  const date = new Date(`${value}T00:00:00.000Z`)
  return !Number.isNaN(date.getTime()) && date.toISOString().slice(0, 10) === value
}

function isDateTime(value: string) {
  return !Number.isNaN(new Date(value).getTime())
}