import type { OpenRequest, PanelInputs, PanelKind, Slot } from "./layout.ts";

/**
 * Where a panel's UI renders. `chrome` panels draw on the shell's top-level origin from data the
 * shell parses (file trees, terminal bytes, transcripts). `sandbox` panels render guest UI, so they
 * must be a sandbox origin's iframe (D3, D10). The playground renders both in-page for now.
 */
export type PanelOrigin = "chrome" | "sandbox";

export interface KindSpec<K extends PanelKind> {
  readonly title: (input: PanelInputs[K]) => string;
  /** Identity of the view: opening a panel whose key is already open activates that panel. */
  readonly key: (input: PanelInputs[K]) => string;
  readonly slot: Slot;
  readonly origin: PanelOrigin;
  /** What each of the input's fields holds, checked when a stored layout is parsed. */
  readonly fields: FieldTypes<PanelInputs[K]>;
}

type FieldTypes<I> = { readonly [F in keyof I]-?: null extends I[F] ? "string | null" : "string" };

export type Kinds = { readonly [K in PanelKind]: KindSpec<K> };

const basename = (path: string) => path.slice(path.lastIndexOf("/") + 1) || path;

export const kinds: Kinds = {
  explorer: { title: () => "Explorer", key: (input) => input.root, slot: "primary", origin: "chrome", fields: { root: "string" } },
  editor: { title: (input) => basename(input.path), key: (input) => input.path, slot: "main", origin: "sandbox", fields: { path: "string" } },
  preview: { title: (input) => `Preview ${basename(input.path)}`, key: (input) => input.path, slot: "main", origin: "sandbox", fields: { path: "string" } },
  terminal: { title: () => "Terminal", key: (input) => input.session, slot: "panel", origin: "chrome", fields: { cwd: "string", session: "string" } },
  agent: { title: () => "Agent", key: (input) => input.conversation, slot: "secondary", origin: "chrome", fields: { conversation: "string" } },
  processes: { title: () => "Processes", key: (input) => input.sandbox, slot: "panel", origin: "chrome", fields: { sandbox: "string" } },
  // One panel per server: another path on the same origin is the same page navigated. The unbound
  // preview's key is empty, which no origin is.
  browser: {
    title: (input) => (input.url === null ? "Preview" : (URL.parse(input.url)?.host ?? input.url)),
    key: (input) => (input.url === null ? "" : (URL.parse(input.url)?.origin ?? input.url)),
    slot: "main",
    origin: "sandbox",
    fields: { url: "string | null" },
  },
};

export function isKind(value: unknown): value is PanelKind {
  return typeof value === "string" && Object.hasOwn(kinds, value);
}

export function spec<K extends PanelKind>(kind: K): KindSpec<K> {
  return kinds[kind];
}

export function keyOf(request: OpenRequest): string {
  return (spec(request.kind).key as (input: OpenRequest["input"]) => string)(request.input);
}

export function titleOf(request: OpenRequest): string {
  return (spec(request.kind).title as (input: OpenRequest["input"]) => string)(request.input);
}