1 files changed, 433 insertions, 0 deletions
diff --git a/srs-anywhere.js b/srs-anywhere.js
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+++ b/srs-anywhere.js
@@ -0,0 +1,433 @@
+/* Copyright © 2025 Jakob L. Kreuze
+
+   This file is part of SRS Anywhere.
+
+   SRS Anywhere is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as
+   published by the Free Software Foundation, either version 3 of the
+   License, or (at your option) any later version.
+
+   SRS Anywhere is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+   Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public
+   License along with SRS Anywhere. If not, see <https://www.gnu.org/licenses/>. */
+
+function reportException(e) {
+  const error = e instanceof Error ? e : new Error(e.toString());
+  console.log(JSON.stringify(error.stack));
+  showToast(`An error has occurred!\n\n${error}\n\n${error.stack}`);
+}
+
+/***********************************************************************
+ * Actual FSRS5 algorithm                                              *
+ ***********************************************************************/
+
+const W = [
+  0.40255, 1.18385, 3.173, 15.69105, 7.1949, 0.5345, 1.4604, 0.0046, 1.54575, 0.1192, 1.01925,
+  1.9395, 0.11, 0.29605, 2.2698, 0.2315, 2.9898, 0.51655, 0.6621,
+];
+
+const F = 19.0 / 81.0;
+const C = -0.5;
+
+const Grade = {
+  forgot: 1.0,
+  hard: 2.0,
+  good: 3.0,
+  easy: 4.0
+};
+
+function retrievability(t, s) {
+  return Math.pow(1.0 + F * (t / s), C);
+}
+
+function interval(r_d, s) {
+  return (s / F) * (Math.pow(r_d, 1.0 / C) - 1.0);
+}
+
+function s_0(g) {
+  switch (g) {
+  case Grade.forgot: return W[0];
+  case Grade.hard: return W[1];
+  case Grade.good: return W[2];
+  case Grade.easy: return W[3];
+  }
+}
+
+function s_success(d, s, r, g) {
+  const t_d = 11.0 - d;
+  const t_s = Math.pow(s, -W[9]);
+  const t_r = Math.exp(W[10] * (1.0 - r)) - 1.0;
+  const h = g === Grade.hard ? W[15] : 1.0;
+  const b = g === Grade.easy ? W[16] : 1.0;
+  const c = Math.exp(W[8]);
+  const alpha = 1.0 + t_d * t_s * t_r * h * b * c;
+  return s * alpha;
+}
+
+function s_fail(d, s, r) {
+  const d_f = Math.pow(d, -W[12]);
+  const s_f = Math.pow(s + 1.0, W[13]) - 1.0;
+  const r_f = Math.exp(W[14] * (1.0 - r));
+  const c_f = W[11];
+  const result = d_f * s_f * r_f * c_f;
+  return Math.min(result, s);
+}
+
+function stability(d, s, r, g) {
+  return g === Grade.forgot ? s_fail(d, s, r) : s_success(d, s, r, g);
+}
+
+function clamp_d(d) {
+  return Math.min(10.0, Math.max(1.0, d));
+}
+
+function d_0(g) {
+  return clamp_d(W[4] - Math.exp(W[5] * (g - 1.0)) + 1.0);
+}
+
+function difficulty(d, g) {
+  return clamp_d(W[7] * d_0(Grade.easy) + (1.0 - W[7]) * dp(d, g));
+}
+
+function dp(d, g) {
+  return d + delta_d(g) * ((10.0 - d) / 9.0);
+}
+
+function delta_d(g) {
+  return -W[6] * (g - 3.0);
+}
+
+function sim(grades) {
+  let t = 0.0;
+  const r_d = 0.9;
+  const steps = [];
+
+  // Initial review
+  if (grades.length === 0) {
+    throw new Error("Grades cannot be empty");
+  }
+
+  let gradesCopy = [...grades];
+  let g = gradesCopy.shift(); // Remove the first grade
+  let s = s_0(g);
+  let d = d_0(g);
+  let i = Math.max(Math.round(interval(r_d, s)), 1.0);
+
+  steps.push({ t, s, d, i });
+
+  // n-th review
+  for (let g of gradesCopy) {
+    t += i;
+    const r = retrievability(i, s);
+    s = stability(d, s, r, g);
+    d = difficulty(d, g);
+    i = Math.max(Math.round(interval(r_d, s)), 1.0);
+    steps.push({ t, s, d, i });
+  }
+
+  return steps;
+}
+
+/***********************************************************************
+ * State file processing                                               *
+ ***********************************************************************/
+
+function statusString() {
+  const now = Date.now();
+  const elapsedSeconds = Math.floor((now - window.started) / 1000);
+  const minutes = Math.floor(elapsedSeconds / 60);
+  const seconds = elapsedSeconds % 60;
+  const pad = (n) => n < 10 ? '0' + n : n;
+  return `Card ${window.index + 1} of ${window.cards.length} scheduled for review, ${window.allCards.length} total
+Current session: ${pad(minutes)}:${pad(seconds)}`;
+}
+
+function loadCard(card) {
+  window.card.revealed = false;
+  window.card.front.innerHTML = card.front;
+  window.card.front.style.display = "block";
+  window.card.back.innerHTML = card.back;
+  window.card.back.style.display = "none";
+  window.buttons.style.display = "none";
+}
+
+function flipCard() {
+  if (window.index >= window.cards.length) {
+    return;
+  }
+
+  window.card.revealed = true;
+
+  // Reveal the "back".
+  if (window.card.front.style.display !== "block") {
+    window.card.front.style.display = "block";
+    window.card.back.style.display = "none";
+  } else {
+    window.card.front.style.display = "none";
+    window.card.back.style.display = "block";
+  }
+
+  // Reveal the buttons.
+  window.buttons.style.display = "flex";
+}
+
+function endReview() {
+  clearInterval(window.updateInterval);
+  window.statusInfo.innerHTML = "Session complete!";
+  window.flashcard.style.display = "none";
+  window.buttons.style.display = "none";
+  updateAllCards();
+  downloadJSON(window.allCards);
+}
+
+function rateCard(difficulty) {
+  if (!window.card.revealed) {
+    return;
+  }
+
+  const card = window.cards[window.index];
+
+  const r_d = 0.9;
+  const s = card._scheduler.s;
+  const d = card._scheduler.d;
+  const i = card._scheduler.i;
+  const g = card._flagged ? Grade.forgot : Grade[difficulty];
+
+  let s_n = undefined, d_n = undefined, i_n = undefined;
+
+  if (s == null || d == null || i == null) {
+    s_n = s_0(g);
+    d_n = d_0(g);
+  } else {
+    const r = retrievability(i, s);
+    s_n = stability(d, s, r, g);
+    d_n = difficulty(d, g);
+  }
+  i_n = Math.max(Math.round(interval(r_d, s)), 1.0);
+
+  let scheduled = today();
+  scheduled.setDate(scheduled.getDate() + i_n);
+
+  if (difficulty === "forgot") {
+    // Shift forgotten card to end.
+    window.cards.push(card);
+    window.cards.splice(window.index, 1);
+    loadCard(window.cards[window.index]);
+  } else {
+    // Unflag and update scheduler parameters.
+    delete card._flagged;
+    card._scheduler.s = s_n;
+    card._scheduler.d = d_n;
+    card._scheduler.i = i_n;
+    card._scheduled = scheduled;
+
+    if (++window.index < window.cards.length) {
+      loadCard(window.cards[window.index]);
+    } else {
+      endReview();
+    }
+  }
+}
+
+// Update `window.allCards` with new scheduler parameters.
+function updateAllCards() {
+  for (let i = 0; i < window.allCards.length; i++) {
+    const updated = window.cards.find((card) => card.id == window.allCards[i].id);
+    if (updated) {
+      window.allCards[i] = updated;
+    }
+  }
+}
+
+function downloadJSON(obj) {
+  // Convert the object to a JSON string (with default formatting)
+  const jsonString = JSON.stringify(obj, null, 2); // 'null, 2' adds indentation for readability
+
+  // Create a Blob with the JSON content
+  const blob = new Blob([jsonString], { type: 'application/json' });
+
+  // Generate a URL for the Blob
+  const url = URL.createObjectURL(blob);
+
+  // Create an anchor element
+  const a = document.createElement('a');
+  a.href = url;
+  a.download = 'data.json'; // Default filename
+
+  // Append the anchor to the body (required for some browsers)
+  document.body.appendChild(a);
+
+  // Simulate a click on the anchor to trigger the download
+  a.click();
+
+  // Clean up
+  document.body.removeChild(a);
+  URL.revokeObjectURL(url);
+}
+
+function today() {
+  let today = new Date();
+  today.setHours(0, 0, 0, 0);
+  return today;
+}
+
+function checkCards(cards) {
+  for (let i = 0; i < cards.length; i++) {
+    const card = cards[i];
+    if (!card.id) {
+      throw new Error("malformed card: missing id")
+    } else if (!card.front) {
+      throw new Error(`malformed card ${card.id}: missing front`)
+    } else if (!card.back) {
+      throw new Error(`malformed card ${card.id}: missing bacak`)
+    }
+    if (!card._scheduled) {
+      card._scheduled = today().toJSON();
+    }
+    if (!card._scheduler) {
+      card._scheduler = {
+        s: null,
+        d: null,
+        i: null
+      }
+    }
+  }
+}
+
+function shuffleArray(array) {
+  let currentIndex = array.length;
+  let randomIndex;
+
+  // While there remain elements to shuffle.
+  while (currentIndex !== 0) {
+    // Pick a remaining element.
+    randomIndex = Math.floor(Math.random() * currentIndex);
+    currentIndex--;
+
+    // And swap it with the current element.
+    [array[currentIndex], array[randomIndex]] = [
+      array[randomIndex],
+      array[currentIndex],
+    ];
+  }
+
+  return array;
+}
+
+function loadCards(data) {
+  checkCards(data);
+
+  document.getElementById('flashcard').style.display = "block";
+
+  window.allCards = data;
+  window.index = 0;
+  window.started = Date.now();
+  window.statusInfo = document.getElementById('status-info');
+  window.buttons = document.getElementById('button-container');
+  window.card = {
+    front: document.getElementById('flashcard-front'),
+    back: document.getElementById('flashcard-back')
+  };
+
+  document.getElementById('rating-button-forgot')
+    .addEventListener('click', () => rateCard('forgot'));
+  document.getElementById('rating-button-hard')
+    .addEventListener('click', () => rateCard('hard'));
+  document.getElementById('rating-button-good')
+    .addEventListener('click', () => rateCard('good'));
+  document.getElementById('rating-button-easy')
+    .addEventListener('click', () => rateCard('easy'));
+
+  let today = new Date();
+  // Granularity only at the day level.
+  today.setHours(0, 0, 0, 0);
+  window.cards = data.filter((card) => {
+    return (new Date(card._scheduled)) <= today;
+  });
+  shuffleArray(window.cards);
+
+  loadCard(window.cards[0]);
+
+  window.updateInterval = setInterval(() => {
+    window.statusInfo.innerText = statusString()
+  }, 1000);
+}
+
+/***********************************************************************
+ * Status display                                                      *
+ ***********************************************************************/
+
+function showToast(message, duration = 3000) {
+  const toast = document.getElementById("toast");
+  toast.innerHTML = "<pre>" + message + "</pre>";
+
+  // Show the toast
+  toast.classList.add("show");
+
+  // Hide the toast after specified time
+  setTimeout(() => {
+    toast.classList.remove("show");
+  }, duration);
+}
+
+window.addEventListener("load", (event) => {
+  document.getElementById('cards-input').addEventListener('change', function(event) {
+    const file = event.target.files[0];
+    if (!file) return;
+
+    const reader = new FileReader();
+    reader.onload = function(e) {
+      try {
+        const content = e.target.result;
+        loadCards(JSON.parse(content));
+      } catch (e) {
+        reportException(e);
+      }
+    };
+
+    reader.onerror = function(error) {
+      document.getElementById('result').textContent = "Error reading file: " + error;
+      reportException(error);
+    };
+
+    reader.readAsText(file); // Read the file as text
+  });
+
+  document.getElementById('flashcard').addEventListener('click', function(event) {
+    flipCard();
+  });
+
+  const modal = document.getElementById('modal');
+  const openBtn = document.getElementById('open-modal');
+  const closeBtn = document.getElementById('close-modal');
+
+  // Show the modal when "Open Modal" is clicked
+  openBtn.addEventListener('click', () => {
+    modal.style.display = 'block';
+  });
+
+  // Hide the modal when "OK" is clicked
+  closeBtn.addEventListener('click', () => {
+    modal.style.display = 'none';
+  });
+});
+
+window.addEventListener('keydown', (event) => {
+  if (event.code === 'Space') {
+    flipCard();
+  } else if (event.code === 'Digit1' || event.code === "Numpad1") {
+    rateCard('forgot');
+  } else if (event.code === 'Digit2' || event.code === "Numpad2") {
+    rateCard('easy');
+  } else if (event.code === 'Digit3' || event.code === "Numpad3") {
+    rateCard('good');
+  } else if (event.code === 'Digit4' || event.code === "Numpad4") {
+    rateCard('hard');
+  } else if (event.code === 'KeyQ') {
+    endReview();
+  }
+});