#!/usr/bin/env node

/**
 * Strict, transactional CSV -> Parquet builder for v0.4.0.
 *
 * Source validation runs before any output is touched. Conversion rejects
 * malformed booleans, numbers, integers and dates rather than silently
 * coercing or dropping them. A completed build replaces parquet/ atomically.
 */

import fs from "node:fs/promises";
import path from "node:path";
import { createHash } from "node:crypto";
import { createRequire } from "node:module";
import { spawnSync } from "node:child_process";
import { fileURLToPath } from "node:url";

const RELEASE_VERSION = "0.4.0";
const require = createRequire(import.meta.url);
let parquet;
let parquetPackage;
try {
  parquet = require("parquetjs-lite");
  parquetPackage = require("parquetjs-lite/package.json");
} catch (caught) {
  throw new Error("Missing pinned dependency parquetjs-lite. Run npm ci from the package root before rebuilding Parquet files.", { cause: caught });
}

const here = path.dirname(fileURLToPath(import.meta.url));
const root = path.resolve(here, "..");
const dataDir = path.join(root, "data");
const outDir = path.join(root, "parquet");
const validator = path.join(here, "validate-data.mjs");

const preflight = spawnSync(process.execPath, [validator, dataDir, "--source-only"], {
  cwd: root,
  encoding: "utf8",
  maxBuffer: 32 * 1024 * 1024
});
if (preflight.error) throw new Error(`Source validation could not run: ${preflight.error.message}`);
if (preflight.status !== 0) {
  const detail = String(preflight.stdout || preflight.stderr || "unknown validation error").trim();
  throw new Error(`Source validation failed; existing Parquet files were not touched.\n${detail}`);
}

function sha256(value) {
  return createHash("sha256").update(value).digest("hex");
}

function canonicalJson(value) {
  if (Array.isArray(value)) return `[${value.map(canonicalJson).join(",")}]`;
  if (value && typeof value === "object") {
    return `{${Object.keys(value).sort().map((key) => `${JSON.stringify(key)}:${canonicalJson(value[key])}`).join(",")}}`;
  }
  return JSON.stringify(value);
}

function parseCsv(text, filename) {
  const input = text.replace(/^\uFEFF/, "");
  const records = [];
  let record = [];
  let field = "";
  let quoted = false;
  for (let index = 0; index < input.length; index += 1) {
    const char = input[index];
    if (quoted) {
      if (char === '"' && input[index + 1] === '"') { field += '"'; index += 1; }
      else if (char === '"') quoted = false;
      else field += char;
    } else if (char === '"' && field === "") quoted = true;
    else if (char === ",") { record.push(field); field = ""; }
    else if (char === "\n") { record.push(field.replace(/\r$/, "")); records.push(record); record = []; field = ""; }
    else if (char === '"') throw new Error(`${filename}: quote inside an unquoted field`);
    else field += char;
  }
  if (quoted) throw new Error(`${filename}: CSV ends inside a quoted field`);
  if (field || record.length) { record.push(field.replace(/\r$/, "")); records.push(record); }
  while (records.length && records.at(-1).every((value) => value === "")) records.pop();
  const headers = records.shift() || [];
  if (!headers.length) throw new Error(`${filename}: missing header row`);
  if (new Set(headers).size !== headers.length) throw new Error(`${filename}: duplicate header`);
  return {
    headers,
    rows: records.filter((row) => row.some((value) => value !== "")).map((values, index) => {
      if (values.length !== headers.length) {
        throw new Error(`${filename}:${index + 2}: expected ${headers.length} fields, found ${values.length}`);
      }
      return Object.fromEntries(headers.map((header, column) => [header, values[column]]));
    })
  };
}

function parquetType(field) {
  if (field.type === "integer") return "INT64";
  if (field.type === "number") return "DOUBLE";
  if (field.type === "boolean") return "BOOLEAN";
  if (field.type === "date") return "DATE";
  if (field.type === "string") return "UTF8";
  throw new Error(`Unsupported datapackage type ${JSON.stringify(field.type)} for ${field.name}`);
}

function isoDate(value, label) {
  const match = /^(\d{4})-(\d{2})-(\d{2})$/.exec(value);
  if (!match) throw new Error(`${label}: invalid ISO date ${JSON.stringify(value)}`);
  const date = new Date(`${value}T00:00:00.000Z`);
  if (
    Number.isNaN(date.valueOf()) ||
    date.getUTCFullYear() !== Number(match[1]) ||
    date.getUTCMonth() + 1 !== Number(match[2]) ||
    date.getUTCDate() !== Number(match[3])
  ) throw new Error(`${label}: invalid calendar date ${JSON.stringify(value)}`);
  return date;
}

function convert(value, field, label) {
  if (value === "" || value === null || value === undefined) return undefined;
  const text = String(value);
  if (field.type === "string") return text;
  if (field.type === "integer") {
    if (!/^[+-]?\d+$/.test(text)) throw new Error(`${label}: invalid integer ${JSON.stringify(text)}`);
    const parsed = Number(text);
    if (!Number.isSafeInteger(parsed)) throw new Error(`${label}: integer exceeds JavaScript safe range ${JSON.stringify(text)}`);
    return parsed;
  }
  if (field.type === "number") {
    if (!/^[+-]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][+-]?\d+)?$/.test(text)) {
      throw new Error(`${label}: invalid number ${JSON.stringify(text)}`);
    }
    const parsed = Number(text);
    if (!Number.isFinite(parsed)) throw new Error(`${label}: non-finite number ${JSON.stringify(text)}`);
    return parsed;
  }
  if (field.type === "boolean") {
    const trueValues = Array.isArray(field.trueValues) && field.trueValues.length ? field.trueValues.map(String) : ["true"];
    const falseValues = Array.isArray(field.falseValues) && field.falseValues.length ? field.falseValues.map(String) : ["false"];
    if (trueValues.includes(text)) return true;
    if (falseValues.includes(text)) return false;
    throw new Error(`${label}: invalid boolean ${JSON.stringify(text)}; expected ${[...trueValues, ...falseValues].join("|")}`);
  }
  if (field.type === "date") return isoDate(text, label);
  throw new Error(`${label}: unsupported type ${JSON.stringify(field.type)}`);
}

const datapackageBuffer = await fs.readFile(path.join(dataDir, "datapackage.json"));
const pkg = JSON.parse(datapackageBuffer.toString("utf8"));
if (pkg.version !== RELEASE_VERSION) {
  throw new Error(`datapackage.json version must be ${RELEASE_VERSION}; found ${pkg.version ?? "missing"}`);
}
if (!Array.isArray(pkg.resources) || pkg.resources.length !== 26) {
  throw new Error(`datapackage.json must declare exactly 26 resources; found ${pkg.resources?.length ?? "invalid"}`);
}

const tempDir = await fs.mkdtemp(path.join(root, ".parquet-build-"));
let installed = false;
try {
  const tables = [];
  for (const resource of pkg.resources) {
    if (!resource || typeof resource.name !== "string" || resource.path !== `${resource.name}.csv`) {
      throw new Error(`Invalid resource name/path declaration: ${JSON.stringify(resource?.name)}`);
    }
    const sourcePath = path.join(dataDir, resource.path);
    const sourceBuffer = await fs.readFile(sourcePath);
    const parsed = parseCsv(sourceBuffer.toString("utf8"), resource.path);
    const fields = resource.schema?.fields;
    if (!Array.isArray(fields)) throw new Error(`${resource.name}: schema.fields is missing`);
    const declaredHeaders = fields.map((field) => field.name);
    if (parsed.headers.length !== declaredHeaders.length || parsed.headers.some((header, index) => header !== declaredHeaders[index])) {
      throw new Error(`${resource.name}: CSV header/order differs from datapackage schema`);
    }

    const parquetSchema = new parquet.ParquetSchema(Object.fromEntries(fields.map((field) => [
      field.name,
      { type: parquetType(field), optional: field.constraints?.required !== true }
    ])));
    const filename = `${resource.name}.parquet`;
    const output = path.join(tempDir, filename);
    const writer = await parquet.ParquetWriter.openFile(parquetSchema, output);
    try {
      for (const [rowIndex, sourceRow] of parsed.rows.entries()) {
        const row = {};
        for (const field of fields) {
          const value = convert(sourceRow[field.name], field, `${resource.path}:${rowIndex + 2}:${field.name}`);
          if (value !== undefined) row[field.name] = value;
        }
        await writer.appendRow(row);
      }
    } finally {
      await writer.close();
    }
    const outputBuffer = await fs.readFile(output);
    tables.push({
      table: resource.name,
      rows: parsed.rows.length,
      file: `parquet/${filename}`,
      bytes: outputBuffer.byteLength,
      sha256: sha256(outputBuffer),
      source_csv: `data/${resource.path}`,
      source_csv_sha256: sha256(sourceBuffer),
      schema_sha256: sha256(Buffer.from(canonicalJson(fields)))
    });
  }

  const manifest = {
    manifest_version: 1,
    dataset_version: RELEASE_VERSION,
    generator: {
      name: "scripts/build-parquet.mjs",
      version: RELEASE_VERSION,
      node: process.version,
      parquetjs_lite: parquetPackage.version
    },
    datapackage_sha256: sha256(datapackageBuffer),
    tables
  };
  await fs.writeFile(path.join(tempDir, "manifest.json"), `${JSON.stringify(manifest, null, 2)}\n`);

  const backupDir = await fs.mkdtemp(path.join(root, ".parquet-backup-"));
  await fs.rm(backupDir, { recursive: true });
  let backedUp = false;
  try {
    try {
      await fs.rename(outDir, backupDir);
      backedUp = true;
    } catch (caught) {
      if (caught.code !== "ENOENT") throw caught;
    }
    await fs.rename(tempDir, outDir);
    installed = true;
    if (backedUp) await fs.rm(backupDir, { recursive: true, force: true });
  } catch (caught) {
    if (backedUp) {
      await fs.rm(outDir, { recursive: true, force: true });
      await fs.rename(backupDir, outDir);
    }
    throw caught;
  }

  process.stdout.write(`${JSON.stringify({
    version: RELEASE_VERSION,
    tables: tables.length,
    rows: tables.reduce((sum, item) => sum + item.rows, 0),
    generator: manifest.generator
  })}\n`);
} finally {
  if (!installed) await fs.rm(tempDir, { recursive: true, force: true });
}