import { Signal } from "@char/aftercare";
import type { JsonValue } from "@berry/api";
import type { ConfigurationContext, ConfigurationSchema, FieldSchema } from "@berry/api/web.ts";
import { extensionRenderers } from "./renderers.ts";
import { folderInput, type FolderOptions } from "./folders.tsx";
import type { ProjectIndex } from "@berry/api/projects.ts";
import { api, watch } from "./client.ts";
import type { Shared } from "./conversation.tsx";
import { modelKey } from "./settings.tsx";
import { computed, type Scope } from "./ui.ts";

export type { ConfigurationSchema, FieldSchema } from "@berry/api/web.ts";
type Values = Record<string, JsonValue>;
export type ConfigurationLocation = Pick<
  ConfigurationContext,
  "tid" | "model" | "request" | "command"
>;

/** Bind custom or generated controls to configuration values and the selected model. */
export function configurationControls(
  scope: Scope,
  name: string,
  schema: ConfigurationSchema,
  location: Signal<ConfigurationLocation>,
  values: Signal<Values | null>,
  apply: (patch: Values) => Values,
  generated: (save: (patch: Values) => Promise<Values>) => HTMLElement,
  status?: Signal<{ pending: number; error: string | null }>,
): HTMLElement {
  const view = extensionRenderers(name)?.configuration?.();
  let form: HTMLElement | undefined;
  let disposed = false;
  let error: string | null = null;
  const renderDefault = () => form ??= generated(save);
  const draw = () => {
    if (disposed) return;
    view?.update({
      ...location.get(),
      extension: name,
      schema,
      values: values.get(),
      saveStatus: status?.get().pending
        ? "saving"
        : error || status?.get().error
        ? "error"
        : "idle",
      error: error ?? status?.get().error ?? null,
      save: async (patch) => {
        await save(patch);
      },
      renderDefault,
    });
  };
  const save = (patch: Values): Promise<Values> => {
    if (disposed || values.get() === null) {
      return Promise.reject(new Error("Configuration is not available."));
    }
    error = null;
    try {
      // draft answers must be updated before a synchronous form submission can read them
      const next = apply(patch);
      values.set(next);
      draw();
      return Promise.resolve(next);
    } catch (cause) {
      error = cause instanceof Error ? cause.message : String(cause);
      draw();
      return Promise.reject(cause);
    }
  };
  const element = view ? <div>{view.element}</div> as HTMLElement : renderDefault();
  scope.add(() => {
    disposed = true;
    view?.dispose?.();
  });
  scope.add(location.subscribe(draw).unsubscribe);
  scope.add(values.subscribe(draw).unsubscribe);
  if (status) scope.add(status.subscribe(draw).unsubscribe);
  draw();
  return element;
}

/** Choices a field's schema cannot list, as they are what the server knows now. */
export type LiveChoices = Readonly<Record<string, Signal<readonly string[]>>>;

/** The live choices of an extension's fields: the machines an environment can be, the models a subagent can run on. */
export function liveChoices(
  scope: Scope,
  extension: string,
  shared: Pick<Shared, "machines" | "enabled">,
): LiveChoices {
  if (extension === "environment") return { environment: shared.machines };
  if (extension === "subagent") {
    return { models: computed(scope, [shared.enabled], () => shared.enabled.get().map(modelKey)) };
  }
  return {};
}

/** One question of a configuration: a typebox property, of the few kinds a form draws. */
export function configurationField(
  key: string,
  schema: FieldSchema,
  value: JsonValue | undefined,
  answer: (value: JsonValue) => void,
  live?: { scope: Scope; choices: Signal<readonly string[]> },
  folders?: FolderOptions,
) {
  if (schema.type === "array") return listField(key, schema, value, answer, live);
  const choices = schema.enum ?? schema.anyOf?.map((option) => option.const ?? null);
  const boolean = schema.type === "boolean";
  const numeric = schema.type === "number" || schema.type === "integer";
  const folder = folders ? folderInput(folders) : undefined;
  const input = (live || choices?.every((choice) => typeof choice === "string")
    ? (
      <select>
        {((choices ?? []) as string[]).map((choice) => <option value={choice}>{choice}</option>)}
      </select>
    )
    : folder?.input ?? <input type={boolean ? "checkbox" : numeric ? "number" : "text"} />) as
      | HTMLInputElement
      | HTMLSelectElement;
  // the choices as they are, and the value even once it is not among them, so it still shows
  let selected = "";
  const draw = () => {
    if (!live) return;
    const names = live.choices.get();
    const all = selected === "" || names.includes(selected) ? names : [...names, selected];
    input.replaceChildren(...all.map((name) => <option value={name}>{name}</option>));
    input.value = selected;
  };
  if (live) {
    live.scope.add(live.choices.subscribe(draw).unsubscribe);
    input.addEventListener("change", () => void (selected = input.value));
  }
  if (numeric) (input as HTMLInputElement).step = schema.type === "integer" ? "1" : "any";
  const read = (): JsonValue =>
    boolean
      ? (input as HTMLInputElement).checked
      : numeric
      ? (input as HTMLInputElement).valueAsNumber
      : input.value;
  const update = (value: JsonValue | undefined) => {
    const next = value ?? schema.default ?? null;
    if (boolean) (input as HTMLInputElement).checked = next === true;
    else if (live) {
      selected = next === null ? "" : String(next);
      draw();
    } else input.value = next === null ? "" : String(next);
  };
  update(value);
  input.addEventListener(boolean || choices || live ? "change" : "input", () => answer(read()));
  const label = schema.title ?? key;
  return {
    element: folder
      ? (
        <div class="field" title={schema.description ?? ""}>
          <label htmlFor={folder.input.id}>{label}</label>
          {folder.element}
        </div>
      )
      : (
        <label class={boolean ? "toggle" : "field"} title={schema.description ?? ""}>
          {boolean ? [] : <span>{label}</span>}
          {input}
          {boolean ? label : []}
        </label>
      ),
    input,
    get value() {
      return read();
    },
    update,
  };
}

/** A question with any number of answers among its choices, a box for each. */
function listField(
  key: string,
  schema: FieldSchema,
  value: JsonValue | undefined,
  answer: (value: JsonValue) => void,
  live?: { scope: Scope; choices: Signal<readonly string[]> },
) {
  const fixed = (schema.items?.enum ?? schema.items?.anyOf?.map((option) => option.const) ?? [])
    .filter((choice) => typeof choice === "string");
  const input = <fieldset class="choices" /> as HTMLFieldSetElement;
  let selected: string[] = [];
  const read = () =>
    [...input.querySelectorAll<HTMLInputElement>("input:checked")].map((box) => box.value);
  // the choices as they are, and the answers even once they are not among them, so they still show
  const draw = () => {
    const choices = live?.choices.get() ?? fixed;
    const all = [...choices, ...selected.filter((choice) => !choices.includes(choice))];
    input.replaceChildren(...all.map((choice) => (
      <label class="toggle">
        <input type="checkbox" value={choice} checked={selected.includes(choice)} />
        {choice}
      </label>
    )));
  };
  if (live) live.scope.add(live.choices.subscribe(draw).unsubscribe);
  const update = (value: JsonValue | undefined) => {
    const next = value ?? schema.default;
    selected = Array.isArray(next) ? next.filter((item) => typeof item === "string") : [];
    draw();
  };
  update(value);
  input.addEventListener("change", () => answer(selected = read()));
  return {
    element: (
      <div class="field" title={schema.description ?? ""}>
        <span>{schema.title ?? key}</span>
        {input}
      </div>
    ),
    input,
    get value(): JsonValue {
      return read();
    },
    update,
  };
}

/** A live configuration draft whose edits become events when committed. */
export function configurationEditor(
  scope: Scope,
  tid: string,
  name: string,
  schema: ConfigurationSchema,
  saving: (save: Promise<unknown>) => void,
  live: LiveChoices = {},
  projects?: Signal<ProjectIndex>,
  location = new Signal<ConfigurationLocation>({ tid, model: null }),
) {
  const values = new Signal<Values | null>(null);
  const status = new Signal({ pending: 0, error: null as string | null });
  let current: Values | null = null;
  let tail: Promise<unknown> = Promise.resolve();
  const edits = new Map<string, { value: JsonValue }>();
  const submitted = new Map<string, { value: JsonValue }>();
  const draw = () =>
    values.set(
      current && {
        ...current,
        ...Object.fromEntries([...edits].map(([key, edit]) => [key, edit.value])),
      },
    );
  scope.add(watch<Values | null>(`configuration:${tid}:${name}`, (next) => {
    current = next;
    draw();
  }));
  const element = configurationControls(
    scope,
    name,
    schema,
    location,
    values,
    (patch) => {
      for (const [key, value] of Object.entries(patch)) {
        if (JSON.stringify(value) === JSON.stringify(values.get()?.[key])) continue;
        if (!submitted.has(key) && JSON.stringify(value) === JSON.stringify(current?.[key])) {
          edits.delete(key);
        } else edits.set(key, { value });
      }
      return { ...values.get()!, ...patch };
    },
    (save) =>
      generatedEditor(scope, name, schema, values, save, live, status, () => current, projects),
    status,
  );
  return {
    element,
    commit() {
      const batch = [...edits].filter(([key, edit]) => submitted.get(key) !== edit);
      if (!batch.length) return;
      for (const [key, edit] of batch) submitted.set(key, edit);
      status.set({ pending: status.get().pending + 1, error: null });
      const operation = tail.catch(() => {}).then(() =>
        api<Values>(
          "PATCH",
          `/api/conversations/${tid}/configuration/${encodeURIComponent(name)}`,
          Object.fromEntries(batch.map(([key, edit]) => [key, edit.value])),
        )
      ).then((next) => {
        current = next;
        for (const [key, edit] of batch) {
          if (edits.get(key) === edit) edits.delete(key);
          if (submitted.get(key) === edit) submitted.delete(key);
        }
        draw();
        status.set({ ...status.get(), error: null });
      }).catch((cause) => {
        for (const [key, edit] of batch) {
          if (submitted.get(key) === edit) submitted.delete(key);
        }
        status.set({
          ...status.get(),
          error: cause instanceof Error ? cause.message : String(cause),
        });
        throw cause;
      }).finally(() => status.set({ ...status.get(), pending: status.get().pending - 1 }));
      tail = operation;
      saving(operation);
      return operation;
    },
  };
}

function generatedEditor(
  scope: Scope,
  name: string,
  schema: ConfigurationSchema,
  values: Signal<Values | null>,
  save: (patch: Values) => Promise<Values>,
  live: LiveChoices,
  remote: Signal<{ pending: number; error: string | null }>,
  baseline: () => Values | null,
  projects?: Signal<ProjectIndex>,
) {
  let current: Values | null = null;
  const environment = new Signal("local");
  const status = <p class="configuration-status" role="status" aria-live="polite" /> as HTMLElement;
  const fields = Object.entries(schema.properties).map(([key, schema]) => {
    const choices = live[key];
    const field = configurationField(
      key,
      schema,
      undefined,
      (value) => {
        const field = fields.find((field) => field.key === key)!.field;
        if (
          !field.input.checkValidity() ||
          (typeof value === "number" && !Number.isFinite(value))
        ) {
          status.classList.add("error");
          status.textContent = field.input.validationMessage || "enter a valid number";
          return;
        }
        status.classList.remove("error");
        status.textContent = "";
        const patch: Values = { [key]: value };
        if (name === "environment" && key === "environment") {
          environment.set(String(value));
          fields.find(({ key }) => key === "cwd")?.field.update("");
          patch.cwd = "";
        }
        void save(patch).catch(() => {});
      },
      choices && { scope, choices },
      name === "environment" && key === "cwd"
        ? {
          scope,
          environment,
          projects,
          base: () => {
            const saved = baseline();
            return environment.get() === saved?.environment
              ? String(saved?.cwd || "") || null
              : null;
          },
        }
        : undefined,
    );
    field.input.addEventListener("keydown", (event) => {
      if ((event as KeyboardEvent).key === "Enter") {
        event.preventDefault();
        (document.activeElement as HTMLElement | null)?.blur();
      }
    });
    return { key, field };
  });
  const element = (
    <fieldset class="configuration" disabled>
      {fields.map(({ field }) => field.element)}
      {status}
    </fieldset>
  ) as HTMLFieldSetElement;
  const draw = () => {
    if (!current) return;
    for (const { key, field } of fields) {
      if (!field.input.contains(document.activeElement)) {
        field.update(current[key]);
      }
    }
  };
  scope.add(
    values.subscribeImmediate((values) => {
      current = values;
      if (name === "environment" && values) {
        environment.set(String(values.environment));
      }
      element.disabled = current === null;
      draw();
    }).unsubscribe,
  );
  scope.add(
    remote.subscribeImmediate(({ pending, error }) => {
      status.classList.toggle("error", error !== null);
      status.textContent = error ??
        (pending ? "applying configuration (pending if agent is busy)" : "");
    }).unsubscribe,
  );
  return element;
}