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packages/media/fonts/font-compress/src/bin/printer.md

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+# printer
+
+## Purpose
+
+Stdout / stderr renderers used by the `suaveplan-font-compress` bin. Owns
+the help screen, banner, per-file progress lines (success / skip / error),
+and the end-of-run summary block. Every renderer writes through an injected
+`NodeJS.WritableStream` so a host (test harness, CI dashboard, web preview)
+can capture the output without monkey-patching the global `process.stdout`.
+Lives in its own module so the entry can stay under the AGENTS.md §3 file
+size budget while keeping the operator-visible output independently
+inspectable and unit-testable.
+
+## Features
+
+- `HELP_TEXT` — the full `--help` screen, including every flag in the spec
+  delta plus the exit-code table.
+- `printBanner` — one-shot summary printed before any per-file work,
+  showing input, output, format, and force state.
+- `printSuccessLine` — `✓` line with the family name and either the
+  compressed byte count (`--format=json`) or the compression ratio
+  (`--format=btf`).
+- `printSkipLine` — `⏭` line when an output already exists and `--force`
+  was not set.
+- `printErrorLine` — `✗` line written to stderr with the file basename and
+  the failure message.
+- `printSummary` — block with total / converted / errors / original size /
+  compressed size / ratio / savings, terminated by the output path.
+
+## Usage: Basic
+
+```ts
+import { HELP_TEXT, printBanner, printSummary } from "./printer.js";
+
+process.stdout.write(HELP_TEXT);
+printBanner(process.stdout, "/fonts", "/out", "btf", false);
+printSummary(process.stdout, summary, "/out");
+```
+
+## Usage: Advanced
+
+```ts
+import { Writable } from "node:stream";
+import { printSummary } from "./printer.js";
+
+const chunks: string[] = [];
+const captured = new Writable({
+    write(chunk, _enc, cb) {
+        chunks.push(chunk.toString("utf8"));
+        cb();
+    },
+});
+printSummary(captured, summary, "/out");
+// chunks.join("") now holds the rendered block — assert in tests / pipe
+// to a CI dashboard webhook.
+```
+
+## API Reference
+
+| Name | Signature | Notes |
+|---|---|---|
+| `HELP_TEXT` | `string` | Pre-rendered help screen (ANSI tones included). |
+| `printBanner` | `(stdout, inputPath, outputPath, format, force) => void` | Writes the run-start block. |
+| `printSuccessLine` | `(stdout, font, originalBytes, compressedBytes, format) => void` | Emits `✓` line; format choice changes the tail. |
+| `printSkipLine` | `(stdout, file) => void` | Emits `⏭` for already-existing outputs. |
+| `printErrorLine` | `(stderr, file, message) => void` | Emits `✗` to stderr. |
+| `printSummary` | `(stdout, summary, outputRoot) => void` | Emits the end-of-run block. |
+| `RunSummary` | record | `{ totalFiles, successCount, errorCount, totalOriginalSize, totalCompressedSize }`. |
+
+## Implementation Notes
+
+ANSI tones come from `format-utils.ts` so the palette is single-sourced.
+Every line is composed by `Array#join("\n")` rather than template literals
+with leading newlines — the test harness can split on `\n` and assert on
+exact strings without worrying about stray indentation. The summary block
+always renders the savings percentage even when no bytes were processed
+(`formatSavings` falls back to `"0.0%"` for non-positive inputs) so the
+output shape stays stable when an operator runs the bin against an empty
+directory.