// History: every configuration change, with undo.
import { h, mount, table, time, confirmDialog, modal, errorBox, badge, diffView } from "../ui.js";
import { get, change, can, state } from "../api.js";
import { rerender } from "../app.js";

export async function render(el, params) {
  if (params.id) return entry(el, params.id);
  const hs = await get("/history", { limit: 200 });
  mount(el,
    h("div", { class: "page-head" }, h("div", { class: "grow" }, h("h1", null, "History"),
      h("div", { class: "muted" }, "Every configuration change, newest first. Undo applies a change backwards, if nothing it touched has changed since."))),
    h("div", { class: "panel" }, table([
      { label: "#", render: (e) => h("a", { href: "#/history/" + e.id }, String(e.id)) },
      { label: "When", render: (e) => time(e.time) },
      { label: "By", render: (e) => [e.username, h("span", { class: "muted small" }, " via " + e.via)] },
      { label: "Change", render: (e) => [h("a", { href: "#/history/" + e.id }, e.description),
        e.reverted_by ? [" ", badge("undone by #" + e.reverted_by, "")] : null, e.revert_of ? [" ", badge("undoes #" + e.revert_of, "accent")] : null] },
      can("config", true) ? { label: "", tdClass: "actions-cell", render: (e) => e.reverted_by ? null : h("button", { class: "small reveal", onclick: () => undo(e) }, "Undo") } : null,
    ].filter(Boolean), hs, { empty: "No changes yet." })));
}

async function undo(e) {
  if (!await confirmDialog("Undo change #" + e.id, "Undo “" + e.description + "”? This is recorded as a new change, which can be undone too." + (!state.immediate ? " It is added to your pending changes, to review and apply." : ""), "Undo")) return;
  try {
    // Like any edit: staged for review, or applied at once in live mode.
    await change("POST", "/history/" + e.id + "/revert");
    rerender();
  } catch (err) { modal("Can't undo", errorBox(err)); }
}

async function entry(el, id) {
  const [e, d] = await Promise.all([get("/history/" + id), get("/history/" + id + "/diff").catch(() => null)]);
  mount(el,
    h("nav", { class: "back-link" }, h("a", { href: "#/history" }, "← History")),
    h("div", { class: "page-head" },
      h("div", { class: "grow" }, h("h1", null, "#" + e.id + ": " + e.description),
        h("div", { class: "muted" }, new Date(e.time).toLocaleString(), " by ", e.username, " via ", e.via,
          e.reverted_by ? [" · undone by ", h("a", { href: "#/history/" + e.reverted_by }, "#" + e.reverted_by)] : null,
          e.revert_of ? [" · undoes ", h("a", { href: "#/history/" + e.revert_of }, "#" + e.revert_of)] : null)),
      can("config", true) && !e.reverted_by ? h("div", { class: "actions" }, h("button", { onclick: () => undo(e) }, "Undo")) : null),
    e.changes.map((c) => h("div", { class: "panel" },
      h("h3", null, action(c) + " " + c.kind + " ", h("span", { class: "mono" }, c.label)),
      fieldsTable(c))),
    d ? h("div", { class: "panel" },
      h("h3", null, "Ruleset"),
      h("p", { class: "muted small" }, "What this change did to the ruleset, rendered by this version of Housecarl."),
      diffView(d.diff)) : null);
}

function action(c) {
  if (!c.before) return "Created";
  if (!c.after) return "Deleted";
  return "Changed";
}

// fieldsTable lists the fields that differ (all of them for a create or
// delete). An object within (settings' builtins) is listed by its own
// fields, "builtins.drop_invalid", so only what changed shows.
function fieldsTable(c) {
  const a = flatten(c.before || {}), b = flatten(c.after || {});
  const keys = [...new Set([...Object.keys(a), ...Object.keys(b)])].sort();
  const show = (v, k) => {
    if (v === undefined || v === "") return "–";
    if (k === "options") return v.length ? v.map((o) => o.name + "=" + o.value).join("; ") : "none";
    if (k === "pools") return v.length ? v.map((p) => p.start + "-" + p.end).join(", ") : "none";
    if (k === "probation_seconds") return v ? v + "s" : "default";
    return typeof v === "string" ? v : JSON.stringify(v);
  };
  const rows = keys.filter((k) => k !== "id").filter((k) => JSON.stringify(a[k]) !== JSON.stringify(b[k]) || !c.before || !c.after);
  return table([
    { label: "Field", render: (k) => h("strong", null, k) },
    c.before ? { label: "Before", render: (k) => h("span", { class: "mono small" }, show(a[k], k)) } : null,
    c.after ? { label: c.before ? "After" : "Value", render: (k) => h("span", { class: "mono small" }, show(b[k], k)) } : null,
  ].filter(Boolean), rows);
}

// flatten lifts the fields of objects within an object to dotted keys
// ({builtins: {loopback: true}} → {"builtins.loopback": true}); lists
// stay whole.
function flatten(o, prefix = "", out = {}) {
  for (const [k, v] of Object.entries(o)) {
    if (v && typeof v === "object" && !Array.isArray(v) && Object.keys(v).length) flatten(v, prefix + k + ".", out);
    else out[prefix + k] = v;
  }
  return out;
}