/**
 * Project brief extraction.
 * Closes BETA_LAUNCH_PLAN P3.7.
 *
 * When a user uploads a PDF / .md / .docx / .txt brief file, we extract
 * the text here and store it on `fs_projects.data.plan.brief`. The
 * `buildSystemPrompt` function in `app/api/chat/route.ts` then surfaces
 * it in the [PROJECT BRIEF] block.
 *
 * Supports:
 *   - .txt / .md — read as-is
 *   - .pdf — extract text via pdf.js (no binary install required)
 *   - .docx — extract via unzipper + xml text nodes
 *   - .html / .htm — strip tags
 *
 * 5 MB max, 50 000 chars after extraction (truncated with a note).
 */
import { query } from "@/lib/db-postgres";
import { log } from "@/lib/server/logger";

export const BRIEF_MAX_CHARS = 50_000;
export const BRIEF_MAX_BYTES = 5 * 1024 * 1024;

export type BriefExtractionResult =
  | { ok: true; text: string; truncated: boolean; chars: number }
  | { ok: false; error: string };

/**
 * Extract plain text from a File-like object.
 * Call from `POST /api/projects/[projectId]/documents/upload`.
 */
export async function extractBriefText(
  buffer: Buffer,
  mimeType: string,
  filename: string,
): Promise<BriefExtractionResult> {
  if (buffer.byteLength > BRIEF_MAX_BYTES) {
    return { ok: false, error: `File is too large (max 5 MB)` };
  }

  try {
    let text = "";
    const lower = filename.toLowerCase();

    if (lower.endsWith(".pdf") || mimeType === "application/pdf") {
      text = await extractPdf(buffer);
    } else if (
      lower.endsWith(".docx") ||
      mimeType ===
        "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
    ) {
      text = await extractDocx(buffer);
    } else if (lower.endsWith(".html") || lower.endsWith(".htm")) {
      text = buffer.toString("utf8").replace(/<[^>]+>/g, " ").replace(/\s+/g, " ").trim();
    } else {
      // .txt, .md, plain text
      text = buffer.toString("utf8");
    }

    text = text.trim();
    const truncated = text.length > BRIEF_MAX_CHARS;
    if (truncated) {
      text =
        text.slice(0, BRIEF_MAX_CHARS) +
        `\n\n[Brief truncated at ${BRIEF_MAX_CHARS} chars — upload a shorter document for full coverage]`;
    }

    return { ok: true, text, truncated, chars: text.length };
  } catch (err) {
    return {
      ok: false,
      error: `Extraction failed: ${err instanceof Error ? err.message : String(err)}`,
    };
  }
}

async function extractPdf(buffer: Buffer): Promise<string> {
  // Dynamic import — pdf-parse is a large optional dep.
  // If not installed, fall back to an error message.
  try {
    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const pdfParse = require("pdf-parse") as (
      b: Buffer,
    ) => Promise<{ text: string }>;
    const result = await pdfParse(buffer);
    return result.text;
  } catch (e: unknown) {
    if (
      e instanceof Error &&
      e.message.includes("Cannot find module")
    ) {
      throw new Error(
        "pdf-parse package not installed. Run `npm install pdf-parse` or upload a .txt/.md file instead.",
      );
    }
    throw e;
  }
}

async function extractDocx(buffer: Buffer): Promise<string> {
  try {
    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const { DOMParser } = require("@xmldom/xmldom") as {
      DOMParser: new () => { parseFromString(xml: string, type: string): Document };
    };
    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const unzipper = require("unzipper") as {
      Open: {
        buffer(b: Buffer): Promise<{ files: Array<{ path: string; buffer(): Promise<Buffer> }> }>;
      };
    };

    const directory = await unzipper.Open.buffer(buffer);
    const wordDoc = directory.files.find(
      (f: { path: string }) => f.path === "word/document.xml",
    );
    if (!wordDoc) throw new Error("word/document.xml not found in docx");

    const xmlBuf = await wordDoc.buffer();
    const xml = xmlBuf.toString("utf8");

    const doc = new DOMParser().parseFromString(xml, "text/xml");
    const texts: string[] = [];

    function extractText(node: Node) {
      if (node.nodeType === 3 /* TEXT_NODE */) {
        const t = (node as Text).textContent?.trim();
        if (t) texts.push(t);
      }
      node.childNodes?.forEach((child: Node) => extractText(child));
    }
    extractText(doc);

    return texts.join(" ");
  } catch (e: unknown) {
    if (e instanceof Error && e.message.includes("Cannot find module")) {
      throw new Error(
        "unzipper or @xmldom/xmldom not installed. Upload a .txt or .md file instead.",
      );
    }
    throw e;
  }
}

/**
 * Persist the extracted brief text to `fs_projects.data.plan.brief`.
 * Called by the upload route after extraction succeeds.
 */
export async function persistProjectBrief(
  projectId: string,
  text: string,
  meta: { filename: string; chars: number; truncated: boolean },
): Promise<void> {
  try {
    await query(
      `UPDATE fs_projects
       SET data = jsonb_set(
         data,
         '{plan}',
         COALESCE(data->'plan', '{}'::jsonb)
           || jsonb_build_object(
               'brief', $1::text,
               'briefMeta', $2::jsonb
             ),
         true
       )
       WHERE id = $3`,
      [
        text,
        JSON.stringify({
          ...meta,
          uploadedAt: new Date().toISOString(),
        }),
        projectId,
      ],
    );
    log.info("project brief persisted", { projectId, chars: meta.chars });
  } catch (err) {
    log.error("brief persist failed", {
      projectId,
      err: err instanceof Error ? err.message : String(err),
    });
    throw err;
  }
}