feat(cli): add command-line interface

pyproject.toml

@@ -33,6 +33,9 @@ dependencies = [
     "markdown-it-py>=3.0.0"
 ]
 
+[project.scripts]
+slackify-markdown = "slackify_markdown.cli:main"
+
 [project.urls]
 "Homepage" = "https://github.com/thesmallstar/slackify-markdown-python"
 "Bug Tracker" = "https://github.com/thesmallstar/slackify-markdown-python/issues"

readme.md

@@ -10,10 +10,16 @@ This library converts regular Markdown to Slack-specific markdown, making it eas
 
 ## Installation
 
+**With pip**
 ```bash
 pip install slackify-markdown
 ```
 
+**With uv**
+```bash
+uv add slackify-markdown
+```
+
 ## Usage
 
 ```python
@@ -54,6 +60,16 @@ This is *bold text* and this is _italic text_.
 """
 ```
 
+## Command-line usage
+
+After installation, use the `slackify-markdown` command to convert a file or stdin:
+
+```bash
+slackify-markdown README.md
+slackify-markdown README.md --output README.slack.md
+cat README.md | slackify-markdown
+```
+
 ## Features
 
 - Converts headers to Slack-compatible bold text
@@ -89,4 +105,4 @@ This project is licensed under the MIT License - see the LICENSE file for detail
 
 ## Acknowledgements
 
-Shoutout to [jsarafaj](https://github.com/jsarafajr), his JS library has inspired the code and tests for this package.
+Shoutout to [jsarafaj](https://github.com/jsarafajr), his JS library has inspired the code and tests for this package.

src/slackify_markdown/cli.py

@@ -0,0 +1,78 @@
+from __future__ import annotations
+
+import argparse
+import sys
+from pathlib import Path
+from typing import Sequence, TextIO
+
+from .service import slackify_markdown
+
+
+def build_parser() -> argparse.ArgumentParser:
+    parser = argparse.ArgumentParser(
+        prog="slackify-markdown",
+        description="Convert Markdown to Slack mrkdwn.",
+    )
+    parser.add_argument(
+        "input",
+        nargs="?",
+        type=Path,
+        help="Markdown file to convert. Reads stdin when omitted or set to '-'.",
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        type=Path,
+        help="Write output to this file instead of stdout.",
+    )
+    return parser
+
+
+def read_markdown(input_path: Path | None, stdin: TextIO) -> str:
+    if input_path is None or str(input_path) == "-":
+        return stdin.read()
+
+    try:
+        return input_path.read_text(encoding="utf-8")
+    except OSError as exc:
+        raise RuntimeError(f"cannot read {input_path}: {exc}") from exc
+
+
+def write_output(slack_text: str, output_path: Path | None, stdout: TextIO) -> None:
+    if output_path is None:
+        stdout.write(slack_text)
+        if slack_text and not slack_text.endswith("\n"):
+            stdout.write("\n")
+        return
+
+    try:
+        output_path.write_text(slack_text, encoding="utf-8")
+    except OSError as exc:
+        raise RuntimeError(f"cannot write {output_path}: {exc}") from exc
+
+
+def run(
+    argv: Sequence[str] | None = None,
+    *,
+    stdin: TextIO = sys.stdin,
+    stdout: TextIO = sys.stdout,
+    stderr: TextIO = sys.stderr,
+) -> int:
+    args = build_parser().parse_args(argv)
+
+    try:
+        markdown = read_markdown(args.input, stdin)
+        write_output(slackify_markdown(markdown), args.output, stdout)
+    except RuntimeError as exc:
+        print(f"slackify-markdown: {exc}", file=stderr)
+        return 1
+
+    return 0
+
+
+def main() -> None:
+    raise SystemExit(run())
+
+
+if __name__ == "__main__":
+    main()

tests/test_cli.py

@@ -0,0 +1,35 @@
+from io import StringIO
+from pathlib import Path
+
+import pytest
+
+from slackify_markdown.cli import run
+
+
+def test_cli_reads_stdin() -> None:
+    stdout = StringIO()
+
+    exit_code = run([], stdin=StringIO("[Link](https://example.com)"), stdout=stdout)
+
+    assert exit_code == 0
+    assert stdout.getvalue() == "<https://example.com|Link>\n"
+
+
+def test_cli_reads_and_writes_files(tmp_path: Path) -> None:
+    input_path = tmp_path / "input.md"
+    output_path = tmp_path / "output.txt"
+    input_path.write_text("*italic*", encoding="utf-8")
+
+    exit_code = run([str(input_path), "--output", str(output_path)])
+
+    assert exit_code == 0
+    assert output_path.read_text(encoding="utf-8") == "_italic_\n"
+
+
+def test_cli_reports_missing_input() -> None:
+    stderr = StringIO()
+
+    exit_code = run(["missing.md"], stderr=stderr)
+
+    assert exit_code == 1
+    assert "cannot read missing.md" in stderr.getvalue()