import { execFile } from "node:child_process";
import { mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { promisify } from "node:util";
import type { Plugin } from "vite";

const run = promisify(execFile);

/**
 * Dev-only PDF compiler. Uses the same local TeX Live toolchain as the
 * repository Makefile, so dev output is byte-identical to `make`.
 * In production the client falls back to the Worker's /api/pdf route.
 */
export function latexDev(): Plugin {
  return {
    name: "latex-dev-compiler",
    apply: "serve",
    configureServer(server) {
      server.middlewares.use("/local/compile", (req, res) => {
        if (req.method !== "POST") {
          res.statusCode = 405;
          res.end();
          return;
        }
        const chunks: Buffer[] = [];
        req.on("data", (c: Buffer) => chunks.push(c));
        req.on("end", () => {
          void (async () => {
            let dir: string | undefined;
            try {
              const { latex } = JSON.parse(Buffer.concat(chunks).toString("utf8")) as {
                latex: string;
              };
              dir = await mkdtemp(join(tmpdir(), "cvtex-"));
              await writeFile(join(dir, "main.tex"), latex, "utf8");
              await run("pdflatex", ["-interaction=nonstopmode", "-halt-on-error", "main.tex"], {
                cwd: dir,
                timeout: 30_000,
              });
              const pdf = await readFile(join(dir, "main.pdf"));
              res.setHeader("Content-Type", "application/pdf");
              res.end(pdf);
            } catch (err) {
              let log = err instanceof Error ? err.message : String(err);
              if (dir) {
                try {
                  log = (await readFile(join(dir, "main.log"), "utf8")).slice(-4000);
                } catch {
                  /* no log written */
                }
              }
              res.statusCode = 422;
              res.setHeader("Content-Type", "application/json");
              res.end(JSON.stringify({ error: "pdflatex failed", log }));
            } finally {
              if (dir) void rm(dir, { recursive: true, force: true });
            }
          })();
        });
      });
    },
  };
}