import type { AnyTaggedError } from "./error.ts"

export type MatchTaggedErrorHandlers<E extends AnyTaggedError, R> = {
  [Tag in E["tag"]]: (error: Extract<E, { tag: Tag }>) => R
}
export const matchTaggedError = <E extends AnyTaggedError, R>(
  taggedError: E,
  handlers: MatchTaggedErrorHandlers<E, R>,
): R => {
  const handler = handlers[taggedError.tag as E["tag"]]
  if (handler === undefined) {
    throw new Error(`No handler for tag: ${taggedError.tag}`)
  }
  return handler(taggedError as Extract<E, { tag: E["tag"] }>)
}

export type MatchTaggedErrorPartialHandlers<E extends AnyTaggedError, R> = {
  [Tag in E["tag"]]?: ((error: Extract<E, { tag: Tag }>) => R) | undefined
}
type UnhandledTaggedError<E extends AnyTaggedError, H> = Exclude<E, { tag: keyof H }>
export const matchTaggedErrorPartial = <
  E extends AnyTaggedError,
  R,
  const Handlers extends MatchTaggedErrorPartialHandlers<E, R> = MatchTaggedErrorPartialHandlers<
    E,
    R
  >,
>(
  taggedError: E,
  handlers: Handlers,
  fallback: (error: UnhandledTaggedError<E, Handlers>) => R,
): R => {
  const handler = handlers[taggedError.tag as E["tag"]]
  if (handler !== undefined) {
    return handler(taggedError as Extract<E, { tag: E["tag"] }>)
  }
  return fallback(taggedError as UnhandledTaggedError<E, Handlers>)
}