import type { DialogButton, Reply } from "../api/types";

/*
 * Maps a batch of engine replies to a focus-screen layout (docs/mock). Pure function: the engine decides WHAT is
 * asked, this only decides HOW it looks. Unknown shapes fall back to a plain choice / text screen.
 */

export type Step =
  | { kind: "idle"; notes: string[] } // engine is back at the menu: the flow is over
  | { kind: "ack"; text: string[] } // a short confirmation without a question: a toast, then home
  | { kind: "consent"; lead: string[]; title: string; buttons: DialogButton[] }
  | { kind: "crisis"; text: string; buttons: DialogButton[] }
  | { kind: "plan"; lead: string[]; title: string; lines: string[]; buttons: DialogButton[] }
  | { kind: "number"; lead: string[]; title: string; options: DialogButton[] }
  | { kind: "actions"; lead: string[]; title: string; options: DialogButton[] }
  | { kind: "choice"; lead: string[]; title: string; options: DialogButton[]; progress?: Progress; formId?: string }
  | { kind: "text"; lead: string[]; title: string; skip?: DialogButton }
  | Survey
  // A questionnaire stopped: paused by the patient (resume button) or held for a specialist (help button only).
  | { kind: "notice"; text: string[]; primary?: DialogButton; help?: DialogButton };

/** One item of a versioned questionnaire (app/dialog/flows/intake.py → question_reply). */
export interface Survey {
  kind: "survey";
  itemId: string;
  instruction: string[]; // form instruction / recall period above the question
  title: string; // the item text, verbatim
  footnotes: string[]; // «*…» explanations printed under the item on the paper form
  options: DialogButton[];
  input: "choice" | "number" | "hours" | "portions" | "text";
  anchors?: string[]; // «0 — самое плохое», «10 — самое хорошее»: the scale ends as printed in the item
  asOf?: string; // ISO date the recall period counts from
  skip?: DialogButton;
  help?: DialogButton;
  pause?: DialogButton;
}

export interface Progress {
  n: number;
  total: number;
}

// config/texts/dialog.yaml → idle.menu_prompt: the bare menu carries no message of its own.
const MENU_PROMPT = "Чем могу помочь?";
// config/texts/dialog.yaml → scale.question: "{n}/{total}. {text}"
const SCALE_ITEM = /^(\d+)\/(\d+)\.\s+([\s\S]+)$/;
// config/texts/intake.yaml → as_of: "Период отсчитывается от даты начала этого опроса: {day}."
const AS_OF = /^Период отсчитывается[^:]*:\s*(\d{4}-\d{2}-\d{2})\.?$/;
// config/texts/intake.yaml → standard_drinks: printed inside the RUS-AUDIT item 2 instruction; shown as a table.
const DRINKS_START = "Стандартная порция";
const ANCHORS = /^\d+\s*—/;
const IQ = /^iq:[^:]+:([^:]+):(\d+|skip)$/;

const isMenu = (r: Reply) => r.buttons.flat().some((b) => b.data.startsWith("menu:"));
const flat = (r: Reply) => r.buttons.flat();
const paragraphs = (text: string) =>
  text
    .split(/\n\s*\n/)
    .map((p) => p.trim())
    .filter(Boolean);

/** Splits a reply into a title (the actual question) and lead paragraphs above it. */
function titled(texts: string[]): { lead: string[]; title: string; progress?: Progress } {
  const parts = texts.flatMap(paragraphs);
  const last = parts.pop() ?? "";
  const m = SCALE_ITEM.exec(last);
  if (m) return { lead: parts, title: m[3].trim(), progress: { n: Number(m[1]), total: Number(m[2]) } };
  // A long last paragraph is body text, not a heading.
  if (last.length > 220) return { lead: [...parts, last], title: "" };
  return { lead: parts, title: last };
}

function survey(batch: Reply[], qIndex: number): Survey | null {
  const buttons = flat(batch[qIndex]);
  const iq = buttons.map((b) => IQ.exec(b.data)).find(Boolean);
  const help = buttons.find((b) => b.data === "intake:help");
  const pause = buttons.find((b) => b.data === "intake:pause");
  if (!pause || !help) return null;
  // A free-text / numeric item has no answer buttons: the item id is then unknown, the text is still verbatim.
  const itemId = iq?.[1] ?? "";
  const options = buttons.filter((b) => IQ.test(b.data) && !b.data.endsWith(":skip"));
  const skip = buttons.find((b) => b.data.startsWith("iq:") && b.data.endsWith(":skip"));

  let asOf: string | undefined;
  const parts = paragraphs(batch[qIndex].text).filter((p) => {
    const m = AS_OF.exec(p);
    if (m) asOf = m[1];
    return !m;
  });
  const footnotes = parts.filter((p) => p.startsWith("*"));
  const body = parts.filter((p) => !p.startsWith("*"));
  let title = body.pop() ?? "";
  let anchors: string[] | undefined;
  if (ANCHORS.test(title) && body.length) {
    anchors = title.replace(/\.$/, "").split(/,\s*(?=\d+\s*—)/);
    title = body.pop() ?? "";
  }
  const instruction = body
    .map((p) => (p.includes(DRINKS_START) ? p.slice(0, p.indexOf(DRINKS_START)).trim() : p))
    .filter(Boolean);
  // Replies before the question in the same batch (e.g. «invalid answer» note) stay visible above it.
  const before = batch.slice(0, qIndex).map((r) => r.text.trim()).filter(Boolean);

  const input =
    options.length >= 5 && options.every((b) => /^\d{1,2}$/.test(b.label.trim()))
      ? "number"
      : options.length
        ? "choice"
        : skip
          ? "text"
          : // Numeric items carry no buttons: diary alcohol is counted in standard drinks, everything else in hours.
            /порци/i.test(title)
            ? "portions"
            : "hours";
  return { kind: "survey", itemId, instruction: [...before, ...instruction], title, footnotes, options, input, anchors, asOf, skip, help, pause };
}

export function classify(batch: Reply[]): Step | null {
  if (batch.length === 0) return null;

  const crisis = batch.find((r) => r.kind === "crisis");
  if (crisis) return { kind: "crisis", text: crisis.text, buttons: batch.flatMap(flat) };

  if (batch.some(isMenu)) {
    const notes = batch
      .filter((r) => !isMenu(r) || r.text.trim() !== MENU_PROMPT)
      .map((r) => r.text.trim())
      .filter((t) => t && t !== MENU_PROMPT);
    return { kind: "idle", notes };
  }

  const plan = batch.find((r) => r.kind === "safety_plan");
  if (plan) {
    const [title, ...rest] = plan.text.split("\n").map((l) => l.trim());
    const lead = batch.filter((r) => r !== plan).map((r) => r.text);
    return {
      kind: "plan",
      lead,
      title,
      lines: rest.filter(Boolean).map((l) => l.replace(/^[•\-–]\s*/, "")),
      buttons: batch.flatMap(flat),
    };
  }

  // The question is the last reply with buttons; everything before it is context.
  const qIndex = batch.map((r) => r.buttons.length > 0).lastIndexOf(true);
  const texts = batch.map((r) => r.text);
  if (qIndex === -1) {
    // Without buttons the engine waits for free text only when it marks the reply as a question; anything else
    // («отметил приём») is a confirmation.
    if (!batch.some((r) => r.kind === "question")) return { kind: "ack", text: texts.filter(Boolean) };
    const { lead, title } = titled(texts);
    return { kind: "text", lead, title };
  }
  const options = flat(batch[qIndex]);
  const s = survey(batch, qIndex);
  if (s) return s;
  const resume = options.find((b) => b.data === "intake:resume" || b.data === "intake:start");
  const helpOnly = options.length === 1 && options[0].data === "intake:help";
  if ((resume && options.length === 1) || helpOnly)
    return { kind: "notice", text: texts.filter(Boolean), primary: resume, help: helpOnly ? options[0] : undefined };
  const head = titled(texts.slice(0, qIndex + 1));
  const tail = texts.slice(qIndex + 1); // rare: info after the question
  const lead = [...head.lead, ...tail];

  if (options.some((b) => b.data === "consent:yes")) return { kind: "consent", lead, title: head.title, buttons: options };
  if (options.every((b) => b.data.endsWith(":skip")))
    return { kind: "text", lead, title: head.title, skip: options[0] };
  if (options.length >= 5 && options.every((b) => /^\d{1,2}$/.test(b.label.trim())))
    return { kind: "number", lead, title: head.title, options };
  if (options.some((b) => /^med:(taken|skip|side_effects):/.test(b.data)))
    return { kind: "actions", lead, title: head.title, options };
  const formId = /^scale:([^:]+):/.exec(options[0]?.data ?? "")?.[1];
  return { kind: "choice", lead, title: head.title, options, progress: head.progress, formId };
}

/** Blocks of an engine text: «• item» lines become list items; wrapped plain lines are joined into paragraphs. */
export function lines(text: string): { list: boolean; text: string }[] {
  const out: { list: boolean; text: string }[] = [];
  for (const raw of text.split("\n")) {
    const l = raw.trim();
    if (!l) continue;
    if (/^[•\-–]\s+/.test(l)) out.push({ list: true, text: l.replace(/^[•\-–]\s+/, "") });
    else if (out.length && !out[out.length - 1].list && !/[.!?:»)]$/.test(out[out.length - 1].text))
      out[out.length - 1] = { list: false, text: `${out[out.length - 1].text} ${l}` };
    else out.push({ list: false, text: l });
  }
  return out;
}