/**
 * Build-time injector for the Discord Components V2 link embed.
 *
 * Computes the Red plan, no-breaks, "as of today" estimate using the SAME
 * engine the app uses, formats a rich embed, and replaces the
 * __DISCORD_EMBED_JSON__ placeholder in dist/index.html with the final,
 * properly-escaped JSON.
 *
 * Run AFTER `vite build` (see the "build" script in package.json). It is
 * executed with vite-node so it can import the TypeScript engine/config
 * directly, guaranteeing the embed and the app agree.
 *
 * The snapshot reflects the moment of the build. The nightly Gitea workflow
 * rebuilds + redeploys so it stays current.
 */
import { readFileSync, writeFileSync } from "node:fs";
import { fileURLToPath } from "node:url";
import { dirname, resolve } from "node:path";

import { loadConfig } from "../src/configLoader.ts";
import { estimate } from "../src/engine.ts";
import { atMidnight, toISODate } from "../src/dates.ts";

const __dirname = dirname(fileURLToPath(import.meta.url));
const root = resolve(__dirname, "..");

const PLACEHOLDER = "__DISCORD_EMBED_JSON__";
const PLAN_ID = "red";
const ACCENT_COLOR = 0xc8102e; // CMU Tartan red, as a decimal int for Discord.
const SITE_NAME = "CMU Meal Estimator";
const SITE_BLURB =
  "See how many meal blocks and FLEX dollars you should have used by any date.";

/**
 * Absolute URL to the site icon shown in the embed. Discord fetches this over
 * the network, so it must be an absolute, publicly reachable URL. Override it
 * per deployment with the SITE_ICON_URL env var (the Gitea workflow sets this
 * from the deploy path). Falls back to a sensible default.
 */
const SITE_ICON_URL =
  process.env.SITE_ICON_URL ??
  "https://www.andrew.cmu.edu/user/REPLACE_ME/apple-touch-icon.png";

/* ---------- formatting helpers (mirror the app) ---------- */

const fmtBlocksWhole = (n) => Math.round(n).toLocaleString("en-US");
const fmtBlocks = (n) =>
  (Math.round(n * 10) / 10).toLocaleString("en-US", {
    maximumFractionDigits: 1,
  });
const fmtMoney = (n) =>
  `$${n.toLocaleString("en-US", {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2,
  })}`;

function niceDate(d) {
  return d.toLocaleDateString("en-US", {
    weekday: "long",
    month: "long",
    day: "numeric",
    year: "numeric",
  });
}

/* ---------- compute today's Red-plan snapshot ---------- */

function computeEmbed() {
  const raw = JSON.parse(
    readFileSync(resolve(root, "public/config.json"), "utf-8")
  );
  const result = loadConfig(raw);
  if (!result.ok) {
    throw new Error(
      `config.json failed validation:\n  - ${result.errors.join("\n  - ")}`
    );
  }
  const config = result.config;

  const plan = config.plans.find((p) => p.id === PLAN_ID);
  if (!plan) {
    throw new Error(
      `Plan "${PLAN_ID}" not found in config. Available: ${config.plans
        .map((p) => p.id)
        .join(", ")}`
    );
  }

  const today = atMidnight(new Date());
  const r = estimate(config, {
    selectedPlanId: PLAN_ID,
    targetDate: today,
    activeMissingPeriodIds: new Set(),
    extraExcludedDays: 0,
    actualMealBlocks: null,
    actualFlexDollars: null,
  });

  // Where "today" falls relative to the meal window, for friendlier copy.
  const beforeStart = today.getTime() < config.mealStartDate.getTime();
  const afterEnd = today.getTime() > config.mealEndDate.getTime();

  const header = `# ${SITE_NAME}\n${SITE_BLURB}`;

  let body;
  if (beforeStart) {
    body =
      `\n\n**${plan.displayName} plan — not started yet**\n` +
      `The meal period begins ${niceDate(config.mealStartDate)}. ` +
      `You start with **${fmtBlocksWhole(plan.totalMealBlocks)} blocks** and ` +
      `**${fmtMoney(plan.totalFlexDollars)} FLEX**.`;
  } else if (afterEnd) {
    body =
      `\n\n**${plan.displayName} plan — meal period ended**\n` +
      `The period ended ${niceDate(config.mealEndDate)}.`;
  } else {
    body =
      `\n\n**${plan.displayName} plan · as of ${niceDate(today)}**\n` +
      `> 🍴 **Blocks left:** ${fmtBlocksWhole(r.remainingMealBlocks)} of ${fmtBlocksWhole(
        plan.totalMealBlocks
      )}\n` +
      `> 💳 **FLEX left:** ${fmtMoney(r.remainingFlexDollars)} of ${fmtMoney(
        plan.totalFlexDollars
      )}\n` +
      `> 📆 **Suggested pace:** ${fmtBlocks(r.perWeekMealBlocks)} blocks + ${fmtMoney(
        r.perWeekFlexDollars
      )} / week\n` +
      `-# On-pace estimate, no breaks excluded. Adjust your own plan & dates on the site.`;
  }

  const content = header + body;

  // Discord Components V2 payload:
  //   type 17 = Container (carries the accent color)
  //     type 9  = Section (text with a right-aligned accessory)
  //       type 10 = Text Display (the markdown content)
  //       accessory type 11 = Thumbnail (the site icon)
  //     type 14 = Separator
  //     type 10 = Text Display (footer link line)
  const payload = {
    component: {
      type: 17,
      accent_color: ACCENT_COLOR,
      components: [
        {
          type: 9,
          components: [{ type: 10, content }],
          accessory: {
            type: 11,
            media: { url: SITE_ICON_URL },
            description: `${SITE_NAME} icon`,
          },
        },
        { type: 14 },
        {
          type: 10,
          content: `-# 🔗 Open the estimator to pick your own plan, date, and breaks.`,
        },
      ],
    },
  };

  return { payload, meta: { plan: plan.displayName, date: toISODate(today) } };
}

/* ---------- inject into dist/index.html ---------- */

function main() {
  const htmlPath = resolve(root, "dist/index.html");
  let html;
  try {
    html = readFileSync(htmlPath, "utf-8");
  } catch {
    throw new Error(
      `dist/index.html not found. Run "vite build" before this script.`
    );
  }

  if (!html.includes(PLACEHOLDER)) {
    throw new Error(
      `Placeholder ${PLACEHOLDER} not found in dist/index.html. ` +
        `Was index.html changed?`
    );
  }

  const { payload, meta } = computeEmbed();

  // JSON.stringify produces valid, fully-escaped JSON — safe to drop between
  // the <script type="application/json"> tags.
  const json = JSON.stringify(payload, null, 2);

  writeFileSync(htmlPath, html.replace(PLACEHOLDER, json), "utf-8");

  console.log(
    `Injected Discord embed (${meta.plan} plan, as of ${meta.date}) into dist/index.html`
  );
}

main();