Interpolate

1import { readColumn } from "./utils.js";
2
3/**
4 * Replace `{column}` placeholders in a template string with values
5 * from a table row.
6 *
7 * Placeholders use curly braces and support dot-paths for nested
8 * access (e.g. `{meta.score}`). String values are inserted verbatim,
9 * numbers and booleans are stringified, and objects/arrays are
10 * JSON-serialized.
11 *
12 * Unlike fail-fast interpolation, this collects ALL missing columns
13 * and throws a single error listing every unresolvable placeholder.
14 *
15 * @param template - The instruction template (e.g. `"Review {file} for issues"`).
16 * @param row - The table row providing column values.
17 * @returns The interpolated string with all placeholders resolved.
18 * @throws Error listing all missing column paths.
19 */
20export function interpolate(
21  template: string,
22  row: Record<string, unknown>,
23): string {
24  const missing: string[] = [];
25
26  const result = template.replace(/\{([^}]+)\}/g, (_match, rawPath) => {
27    const path = rawPath.trim();
28
29    const value = readColumn(row, path);
30    if (value === undefined) {
31      missing.push(path);
32      return `{${path}}`;
33    }
34
35    if (typeof value === "string") {
36      return value;
37    }
38
39    if (typeof value === "number" || typeof value === "boolean") {
40      return String(value);
41    }
42
43    return JSON.stringify(value);
44  });
45
46  if (missing.length > 0) {
47    throw new Error(
48      `Interpolation failed: missing columns: ${missing.join(", ")}`,
49    );
50  }
51
52  return result;
53}
54
55/**
56 * Extract the unique column paths referenced by `{column}` placeholders
57 * in a template string.
58 *
59 * Preserves first-seen order. Dot-paths are returned as-is (e.g.
60 * `"meta.score"`). Whitespace inside braces is trimmed, matching
61 * `interpolate`'s behavior.
62 *
63 * @param template - Instruction template (e.g. `"Review {file}: {note}"`).
64 * @returns Array of unique placeholder paths in first-seen order.
65 */
66export function extractPlaceholders(template: string): string[] {
67  const seen = new Set<string>();
68  const ordered: string[] = [];
69  const re = /\{([^}]+)\}/g;
70  let m: RegExpExecArray | null = re.exec(template);
71  while (m !== null) {
72    const path = m[1].trim();
73    if (path.length > 0 && !seen.has(path)) {
74      seen.add(path);
75      ordered.push(path);
76    }
77    m = re.exec(template);
78  }
79  return ordered;
80}