49 lines
1.4 KiB
JavaScript
49 lines
1.4 KiB
JavaScript
export class DiffEngine {
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build(oldText, newText) {
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const a = (oldText ?? "").replace(/\r\n/g, "\n").split("\n");
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const b = (newText ?? "").replace(/\r\n/g, "\n").split("\n");
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const lcs = this.#lcsTable(a, b);
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const ops = [];
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let i = 0;
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let j = 0;
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while (i < a.length && j < b.length) {
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if (a[i] === b[j]) {
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ops.push({ kind: "equal", oldLine: a[i], newLine: b[j], oldIndex: i, newIndex: j });
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i += 1;
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j += 1;
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} else if (lcs[i + 1][j] >= lcs[i][j + 1]) {
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ops.push({ kind: "remove", oldLine: a[i], oldIndex: i, newIndex: j });
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i += 1;
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} else {
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ops.push({ kind: "add", newLine: b[j], oldIndex: i, newIndex: j });
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j += 1;
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}
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}
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while (i < a.length) {
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ops.push({ kind: "remove", oldLine: a[i], oldIndex: i, newIndex: j });
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i += 1;
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}
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while (j < b.length) {
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ops.push({ kind: "add", newLine: b[j], oldIndex: i, newIndex: j });
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j += 1;
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}
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return ops.map((op, index) => ({ ...op, id: index }));
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}
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#lcsTable(a, b) {
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const rows = a.length + 1;
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const cols = b.length + 1;
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const table = Array.from({ length: rows }, () => Array(cols).fill(0));
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for (let i = rows - 2; i >= 0; i -= 1) {
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for (let j = cols - 2; j >= 0; j -= 1) {
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if (a[i] === b[j]) table[i][j] = table[i + 1][j + 1] + 1;
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else table[i][j] = Math.max(table[i + 1][j], table[i][j + 1]);
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}
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}
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return table;
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}
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}
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