Initial commit: omp-edit DSH plugin (oh-my-pi port) with docs and tests

lib/diff.js

@@ -0,0 +1,38 @@
+// Hunk diffs for the DSH diff card ({path, oldText, newText} per hunk, 3 lines of context).
+import { lineMap } from './store.js'
+import { splitLines } from './text.js'
+
+export function hunkDiffs(path, before, after, context = 3) {
+  const a = splitLines(before).lines
+  const b = splitLines(after).lines
+  const map = lineMap(a, b)
+  // Walk both sides, emitting ops: '=' common, '-' removed, '+' added.
+  const ops = []
+  let i = 1; let j = 1
+  const pairs = [...map.entries()].sort((x, y) => x[0] - y[0])
+  for (const [ai, bj] of pairs) {
+    while (i < ai) ops.push(['-', a[i++ - 1]])
+    while (j < bj) ops.push(['+', b[j++ - 1]])
+    ops.push(['=', a[i - 1]]); i++; j++
+  }
+  while (i <= a.length) ops.push(['-', a[i++ - 1]])
+  while (j <= b.length) ops.push(['+', b[j++ - 1]])
+  const changed = ops.map((o, k) => (o[0] !== '=' ? k : -1)).filter((k) => k >= 0)
+  if (!changed.length) return []
+  const spans = []
+  for (const k of changed) {
+    const s = Math.max(0, k - context); const e = Math.min(ops.length - 1, k + context)
+    const last = spans.at(-1)
+    if (last && s <= last[1] + 1) last[1] = Math.max(last[1], e)
+    else spans.push([s, e])
+  }
+  return spans.map(([s, e]) => {
+    const oldL = []; const newL = []
+    for (let k = s; k <= e; k++) {
+      const [op, text] = ops[k]
+      if (op !== '+') oldL.push(text)
+      if (op !== '-') newL.push(text)
+    }
+    return { path, oldText: oldL.length ? oldL.join('\n') : null, newText: newL.join('\n') }
+  })
+}