const fs = require('fs');
const path = require('path');

const usersPath = path.resolve(__dirname, 'users.json');

function normalize(value) {
  return String(value ?? '').trim();
}

function unique(values) {
  return [
    ...new Set(
      values
        .map(normalize)
        .filter(Boolean)
    )
  ];
}

function loadUsers() {
  const raw = fs.readFileSync(usersPath, 'utf8');
  const data = JSON.parse(raw);

  if (!data || !Array.isArray(data.users)) {
    throw new Error('Formato users.json non valido');
  }

  return data.users;
}

function findUserByName(userName) {
  const requestedName = normalize(userName).toLowerCase();

  if (!requestedName) {
    return null;
  }

  return (
    loadUsers().find((user) => {
      return normalize(user.name).toLowerCase() === requestedName;
    }) || null
  );
}

function getUserAccess(userName) {
  const user = findUserByName(userName);

  if (!user) {
    return null;
  }

  const devices = Array.isArray(user.devices)
    ? unique(user.devices)
    : [];

  const usersR = Array.isArray(user.usersR)
    ? unique(user.usersR)
    : [];

  const usersW = Array.isArray(user.usersW)
    ? unique(user.usersW)
    : [];

  return {
    id: user.id,
    name: normalize(user.name),
    devices,
    usersR,
    usersW,

    // Contenuti leggibili nella galleria
    readableSources: unique([
      ...usersR,
      ...devices
    ]),

    // Contenuti modificabili
    writableSources: unique([
      ...usersW,
      ...devices
    ])
  };
}

function getReadableSources(userName) {
  const access = getUserAccess(userName);

  return access
    ? access.readableSources
    : [];
}

function getWritableSources(userName) {
  const access = getUserAccess(userName);

  return access
    ? access.writableSources
    : [];
}

function filterReadableSources(userName, requestedSources) {
  const readableSources = getReadableSources(userName);

  if (!requestedSources) {
    return readableSources;
  }

  const requested = Array.isArray(requestedSources)
    ? requestedSources
    : [requestedSources];

  const readableMap = new Map(
    readableSources.map((source) => [
      source.toLowerCase(),
      source
    ])
  );

  return unique(requested)
    .map((source) => {
      return readableMap.get(source.toLowerCase());
    })
    .filter(Boolean);
}

function canRead(userName, sourceName) {
  const source = normalize(sourceName).toLowerCase();

  if (!source) {
    return false;
  }

  return getReadableSources(userName).some((allowedSource) => {
    return allowedSource.toLowerCase() === source;
  });
}

function canWrite(userName, sourceName) {
  const source = normalize(sourceName).toLowerCase();

  if (!source) {
    return false;
  }

  return getWritableSources(userName).some((allowedSource) => {
    return allowedSource.toLowerCase() === source;
  });
}

module.exports = {
  loadUsers,
  findUserByName,
  getUserAccess,
  getReadableSources,
  getWritableSources,
  filterReadableSources,
  canRead,
  canWrite
};