// Pure widget-descriptor builders (spec D2/D4, §4.1).
//
// Each function turns plain params into a ui_request descriptor object. No Pi
// context, no I/O -- this is the part of the gate that is fully testable in L1
// (in JS, in-language, no Python mirror). The glue (emission via ctx.sendRaw,
// anti-bypass, the no-limbo loop) is in tht-gate.js and is verified at L2.
//
// The 6 widget kinds: info, select, multiselect, freetext, artifact-gate, artifact.
// `widget` is an open field (a new kind needs a renderer, not infra changes);
// these are the initial 6. reserved = framework escape hatches always present on
// blocking widgets: back / exit / other.

"use strict";

const SCHEMA_VERSION = 1;
const RESERVED = ["back", "exit", "other"];

const ALTRO_LABEL = "Altro — specifica…";
const VALID_ACTION_KINDS = new Set(["confirm", "approve_reject", "view_only"]);
const VALID_INFO_LEVELS = new Set(["info", "warning", "error"]);

function requireString(value, name, ctx) {
  if (typeof value !== "string" || value.length === 0) {
    throw new Error(`builders: ${ctx} requires a non-empty ${name}`);
  }
  return value;
}

function requireArray(value, name, ctx) {
  if (!Array.isArray(value)) {
    throw new Error(`builders: ${ctx} requires ${name} to be an array`);
  }
  return value;
}

// An "other" option that opens a freetext child widget. Always present on
// blocking pick widgets so the reviewer is never trapped in the listed options.
function altroOption() {
  return {
    id: "other",
    label: ALTRO_LABEL,
    opens: { widget: "freetext", title: "Specifica…" },
  };
}

// Build a `select` ui_request (single-pick). Reserved hatches (Altro/Back/Exit)
// are injected; Altro carries the freetext linkage (§4.2). `recommended` is the
// id of the option to highlight as "(consigliato)".
function buildSelectRequest({
  id, phase, title, options, intro = null, allowOther = true, recommended = null,
}) {
  requireString(title, "title", "select");
  const opts = requireArray(options, "options", "select");
  const out = {
    type: "ui_request",
    id,
    phase,
    schema_version: SCHEMA_VERSION,
    widget: "select",
    title,
    intro,
    allow_other: allowOther,
    recommended,
    options: allowOther ? [...opts, altroOption()] : [...opts],
    reserved: RESERVED,
  };
  return out;
}

// Build a `multiselect` ui_request (multi-pick). `content` is the scrollable
// context (e.g. schema candidates); `selected` the pre-checked option ids;
// `allowEmpty:false` with zero options is a broken widget and throws.
function buildMultiselectRequest({
  id, phase, title, options, content = null, selected = [], allowEmpty = false, allowOther = true,
}) {
  requireString(title, "title", "multiselect");
  const opts = requireArray(options, "options", "multiselect");
  if (!allowEmpty && opts.length === 0) {
    throw new Error(
      "builders: multiselect with allow_empty:false requires at least one option",
    );
  }
  return {
    type: "ui_request",
    id,
    phase,
    schema_version: SCHEMA_VERSION,
    widget: "multiselect",
    title,
    allow_empty: allowEmpty,
    allow_other: allowOther,
    options: [...opts],
    selected: [...selected],
    content,
    reserved: RESERVED,
  };
}

// Build an `artifact-gate` ui_request: a rendered artifact + a disposition list
// (confirm / approve_reject / view_only). The decision is load-bearing on the
// document, so the artifact is never shown alone (spec §4.1).
function buildArtifactGate({ id, phase, title, artifact, action }) {
  requireString(title, "title", "artifact-gate");
  if (!artifact || typeof artifact !== "object") {
    throw new Error("builders: artifact-gate requires an artifact object");
  }
  if (!artifact.kind) {
    throw new Error("builders: artifact-gate artifact requires a kind");
  }
  if (!action || !action.kind || !VALID_ACTION_KINDS.has(action.kind)) {
    throw new Error(
      `builders: artifact-gate action.kind must be one of ${[...VALID_ACTION_KINDS].join(", ")}`,
    );
  }
  return {
    type: "ui_request",
    id,
    phase,
    schema_version: SCHEMA_VERSION,
    widget: "artifact-gate",
    title,
    artifact,
    action,
    reserved: RESERVED,
  };
}

// Build an `info` ui_request: fire-and-forget notification (no response expected,
// no reserved hatches, no correlated id).
function buildInfoRequest({ phase, level, text }) {
  if (!level || !VALID_INFO_LEVELS.has(level)) {
    throw new Error(
      `builders: info level must be one of ${[...VALID_INFO_LEVELS].join(", ")}`,
    );
  }
  requireString(text, "text", "info");
  return {
    type: "ui_request",
    phase,
    schema_version: SCHEMA_VERSION,
    widget: "info",
    level,
    text,
  };
}

// Build a `freetext` ui_request: free-text input, always a child of
// select/artifact-gate (via Altro/Rifiuta) or via the ambient steering channel.
function buildFreetextRequest({ id, phase, title }) {
  requireString(title, "title", "freetext");
  return {
    type: "ui_request",
    id,
    phase,
    schema_version: SCHEMA_VERSION,
    widget: "freetext",
    title,
    reserved: RESERVED,
  };
}

// Attach a child-widget spec to an option (linkage, §4.2). Returns the option.
function withChildLinkage(option, widgetSpec) {
  option.opens = widgetSpec;
  return option;
}

module.exports = {
  buildSelectRequest,
  buildMultiselectRequest,
  buildArtifactGate,
  buildInfoRequest,
  buildFreetextRequest,
  withChildLinkage,
  SCHEMA_VERSION,
  RESERVED,
};