chore(tables): own fractional-indexing in-house, drop runtime dep

apps/sim/lib/fractional-indexing/fractional-indexing.ts

@@ -0,0 +1,281 @@
+/**
+ * Fractional indexing — generate ordering strings that sort lexicographically.
+ *
+ * In-house port of David Greenspan's algorithm
+ * (https://observablehq.com/@dgreensp/implementing-fractional-indexing),
+ * behavior-identical to the `fractional-indexing` npm package (CC0). A key is a
+ * variable-length base-62 string: between any two keys there is always room for
+ * another, so inserts never renumber existing rows. The only cost is gradual
+ * length growth under repeated same-spot inserts.
+ *
+ * A key is `<integer part><fraction>`. The integer part's first character
+ * encodes its own length (`a..z` → 2..27, `A..Z` → 27..2), letting integers
+ * grow without bound in both directions. The fraction is plain base-62 digits
+ * with no trailing zero.
+ */
+
+// ---------------------------------------------------------------------------
+// Digits
+// ---------------------------------------------------------------------------
+
+/** Default digit alphabet. Must be in ascending character-code order. */
+export const BASE_62_DIGITS = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
+
+// ---------------------------------------------------------------------------
+// Integer-part helpers
+// ---------------------------------------------------------------------------
+
+/** Length the integer part must have, derived from its first character. */
+function getIntegerLength(head: string): number {
+  if (head >= 'a' && head <= 'z') {
+    return head.charCodeAt(0) - 'a'.charCodeAt(0) + 2
+  }
+  if (head >= 'A' && head <= 'Z') {
+    return 'Z'.charCodeAt(0) - head.charCodeAt(0) + 2
+  }
+  throw new Error(`invalid order key head: ${head}`)
+}
+
+function validateInteger(int: string): void {
+  if (int.length !== getIntegerLength(int[0])) {
+    throw new Error(`invalid integer part of order key: ${int}`)
+  }
+}
+
+function getIntegerPart(key: string): string {
+  const integerPartLength = getIntegerLength(key[0])
+  if (integerPartLength > key.length) {
+    throw new Error(`invalid order key: ${key}`)
+  }
+  return key.slice(0, integerPartLength)
+}
+
+function validateOrderKey(key: string, digits: string): void {
+  if (key === `A${digits[0].repeat(26)}`) {
+    throw new Error(`invalid order key: ${key}`)
+  }
+  // getIntegerPart throws if the head is bad or the key is too short.
+  const i = getIntegerPart(key)
+  const f = key.slice(i.length)
+  if (f.slice(-1) === digits[0]) {
+    throw new Error(`invalid order key: ${key}`)
+  }
+}
+
+/** Increment the integer part; returns null past the largest integer. */
+function incrementInteger(x: string, digits: string): string | null {
+  validateInteger(x)
+  const [head, ...digs] = x.split('')
+  let carry = true
+  for (let i = digs.length - 1; carry && i >= 0; i--) {
+    const d = digits.indexOf(digs[i]) + 1
+    if (d === digits.length) {
+      digs[i] = digits[0]
+    } else {
+      digs[i] = digits[d]
+      carry = false
+    }
+  }
+  if (carry) {
+    if (head === 'Z') {
+      return `a${digits[0]}`
+    }
+    if (head === 'z') {
+      return null
+    }
+    const h = String.fromCharCode(head.charCodeAt(0) + 1)
+    if (h > 'a') {
+      digs.push(digits[0])
+    } else {
+      digs.pop()
+    }
+    return h + digs.join('')
+  }
+  return head + digs.join('')
+}
+
+/** Decrement the integer part; returns null past the smallest integer. */
+function decrementInteger(x: string, digits: string): string | null {
+  validateInteger(x)
+  const [head, ...digs] = x.split('')
+  let borrow = true
+  for (let i = digs.length - 1; borrow && i >= 0; i--) {
+    const d = digits.indexOf(digs[i]) - 1
+    if (d === -1) {
+      digs[i] = digits.slice(-1)
+    } else {
+      digs[i] = digits[d]
+      borrow = false
+    }
+  }
+  if (borrow) {
+    if (head === 'a') {
+      return `Z${digits.slice(-1)}`
+    }
+    if (head === 'A') {
+      return null
+    }
+    const h = String.fromCharCode(head.charCodeAt(0) - 1)
+    if (h < 'Z') {
+      digs.push(digits.slice(-1))
+    } else {
+      digs.pop()
+    }
+    return h + digs.join('')
+  }
+  return head + digs.join('')
+}
+
+// ---------------------------------------------------------------------------
+// Midpoint
+// ---------------------------------------------------------------------------
+
+/**
+ * Fraction strictly between `a` and `b` (both without integer parts). `a` may be
+ * empty; `b` is null (open end) or non-empty and `> a`. No trailing zeros.
+ */
+function midpoint(a: string, b: string | null | undefined, digits: string): string {
+  const zero = digits[0]
+  if (b != null && a >= b) {
+    throw new Error(`${a} >= ${b}`)
+  }
+  if (a.slice(-1) === zero || (b && b.slice(-1) === zero)) {
+    throw new Error('trailing zero')
+  }
+  if (b) {
+    // Strip the longest common prefix, padding `a` with zeros as we go. `b`
+    // needs no padding — it can't end before `a` within the common prefix.
+    let n = 0
+    while ((a[n] || zero) === b[n]) {
+      n++
+    }
+    if (n > 0) {
+      return b.slice(0, n) + midpoint(a.slice(n), b.slice(n), digits)
+    }
+  }
+  // First digits (or lack thereof) differ.
+  const digitA = a ? digits.indexOf(a[0]) : 0
+  const digitB = b != null ? digits.indexOf(b[0]) : digits.length
+  if (digitB - digitA > 1) {
+    const midDigit = Math.round(0.5 * (digitA + digitB))
+    return digits[midDigit]
+  }
+  // First digits are consecutive.
+  if (b && b.length > 1) {
+    return b.slice(0, 1)
+  }
+  // `b` is null or a single digit; recurse into `a`'s tail.
+  return digits[digitA] + midpoint(a.slice(1), null, digits)
+}
+
+// ---------------------------------------------------------------------------
+// Public API
+// ---------------------------------------------------------------------------
+
+/**
+ * Returns a key that sorts strictly between `a` and `b`. Either may be null for
+ * an open end. `a < b` lexicographically when both are non-null.
+ *
+ * @throws if `a`/`b` are invalid keys or `a >= b`.
+ */
+export function generateKeyBetween(
+  a: string | null | undefined,
+  b: string | null | undefined,
+  digits: string = BASE_62_DIGITS
+): string {
+  if (a != null) {
+    validateOrderKey(a, digits)
+  }
+  if (b != null) {
+    validateOrderKey(b, digits)
+  }
+  if (a != null && b != null && a >= b) {
+    throw new Error(`${a} >= ${b}`)
+  }
+  if (a == null) {
+    if (b == null) {
+      return `a${digits[0]}`
+    }
+    const ib = getIntegerPart(b)
+    const fb = b.slice(ib.length)
+    if (ib === `A${digits[0].repeat(26)}`) {
+      return ib + midpoint('', fb, digits)
+    }
+    if (ib < b) {
+      return ib
+    }
+    const res = decrementInteger(ib, digits)
+    if (res == null) {
+      throw new Error('cannot decrement any more')
+    }
+    return res
+  }
+
+  if (b == null) {
+    const ia = getIntegerPart(a)
+    const fa = a.slice(ia.length)
+    const i = incrementInteger(ia, digits)
+    return i == null ? ia + midpoint(fa, null, digits) : i
+  }
+
+  const ia = getIntegerPart(a)
+  const fa = a.slice(ia.length)
+  const ib = getIntegerPart(b)
+  const fb = b.slice(ib.length)
+  if (ia === ib) {
+    return ia + midpoint(fa, fb, digits)
+  }
+  const i = incrementInteger(ia, digits)
+  if (i == null) {
+    throw new Error('cannot increment any more')
+  }
+  if (i < b) {
+    return i
+  }
+  return ia + midpoint(fa, null, digits)
+}
+
+/**
+ * Returns `n` distinct keys in sorted order, strictly between `a` and `b` (same
+ * open-end semantics as {@link generateKeyBetween}). When both ends are null,
+ * returns a contiguous run of "integer" keys.
+ */
+export function generateNKeysBetween(
+  a: string | null | undefined,
+  b: string | null | undefined,
+  n: number,
+  digits: string = BASE_62_DIGITS
+): string[] {
+  if (n === 0) {
+    return []
+  }
+  if (n === 1) {
+    return [generateKeyBetween(a, b, digits)]
+  }
+  if (b == null) {
+    let c = generateKeyBetween(a, b, digits)
+    const result = [c]
+    for (let i = 0; i < n - 1; i++) {
+      c = generateKeyBetween(c, b, digits)
+      result.push(c)
+    }
+    return result
+  }
+  if (a == null) {
+    let c = generateKeyBetween(a, b, digits)
+    const result = [c]
+    for (let i = 0; i < n - 1; i++) {
+      c = generateKeyBetween(a, c, digits)
+      result.push(c)
+    }
+    result.reverse()
+    return result
+  }
+  const mid = Math.floor(n / 2)
+  const c = generateKeyBetween(a, b, digits)
+  return [
+    ...generateNKeysBetween(a, c, mid, digits),
+    c,
+    ...generateNKeysBetween(c, b, n - mid - 1, digits),
+  ]
+}

apps/sim/lib/table/order-key.ts

@@ -5,12 +5,16 @@
  * between two rows mints a key strictly between their keys, so no other row's
  * key changes — insert and delete become O(1) (no position reshift / recompact).
  *
- * Thin wrapper over `fractional-indexing` (Figma/rocicorp algorithm) so the
- * implementation is swappable. Keys never run out (variable-length strings);
- * the only cost is gradual length growth under repeated same-spot inserts.
+ * Thin wrapper over the in-house fractional-indexing port (Figma/rocicorp
+ * algorithm) so the implementation is swappable. Keys never run out
+ * (variable-length strings); the only cost is gradual length growth under
+ * repeated same-spot inserts.
  */
 
-import { generateKeyBetween, generateNKeysBetween } from 'fractional-indexing'
+import {
+  generateKeyBetween,
+  generateNKeysBetween,
+} from '@/lib/fractional-indexing/fractional-indexing'
 
 /**
  * Returns a key that sorts strictly between `a` and `b`. Pass `null` for an open

apps/sim/package.json

@@ -132,7 +132,6 @@
     "es-toolkit": "1.45.1",
     "ffmpeg-static": "5.3.0",
     "fluent-ffmpeg": "2.1.3",
-    "fractional-indexing": "3.2.0",
     "framer-motion": "^12.5.0",
     "free-email-domains": "1.2.25",
     "google-auth-library": "10.5.0",