add pretty printing for regex patterns

src/pycalver/__main__.py

@@ -9,6 +9,7 @@ __main__ module for PyCalVer.
 
 Enables use as module: $ python -m pycalver --version
 """
+import io
 import sys
 import typing as typ
 import logging
@@ -16,6 +17,7 @@ import datetime as dt
 import subprocess as sp
 
 import click
+import colorama
 
 from . import vcs
 from . import v1cli
@@ -23,6 +25,8 @@ from . import v2cli
 from . import config
 from . import rewrite
 from . import version
+from . import patterns
+from . import regexfmt
 from . import v1rewrite
 from . import v1version
 from . import v2rewrite
@@ -149,7 +153,7 @@ def test(
 ) -> None:
     """Increment a version number for demo purposes."""
     _configure_logging(verbose=max(_VERBOSE, verbose))
-    raw_pattern = pattern
+    raw_pattern = pattern  # use internal naming convention
 
     _validate_release_tag(release)
     _date = _validate_date(date, pin_date)
@@ -491,5 +495,108 @@ def bump(
     _try_bump(cfg, new_version, commit_message, allow_dirty)
 
 
+def _grep_text(pattern: patterns.Pattern, text: str, color: bool) -> int:
+    match_count = 0
+    all_lines   = text.splitlines()
+    for match in pattern.regexp.finditer(text):
+        match_count += 1
+        match_start, match_end = match.span()
+
+        line_idx   = text[:match_start].count("\n")
+        line_start = text.rfind("\n", 0, match_start) + 1
+        line_end   = text.find("\n", match_end, -1)
+        if color:
+            matched_line = (
+                text[line_start:match_start]
+                + colorama.Style.BRIGHT
+                + text[match_start:match_end]
+                + colorama.Style.RESET_ALL
+                + text[match_end:line_end]
+            )
+        else:
+            matched_line = (
+                text[line_start:match_start]
+                + text[match_start:match_end]
+                + text[match_end:line_end]
+            )
+
+        lines_offset = max(0, line_idx - 1) + 1
+        lines        = all_lines[line_idx - 1 : line_idx + 2]
+
+        if line_idx == 0:
+            lines[0] = matched_line
+        else:
+            lines[1] = matched_line
+
+        for i, line in enumerate(lines):
+            print(f"{lines_offset + i:>4}: {line}")
+
+        print()
+    return match_count
+
+
+def _grep(
+    raw_pattern: str,
+    file_ios   : typ.Tuple[io.TextIOWrapper],
+    color      : bool,
+) -> None:
+    pattern = v2patterns.compile_pattern(raw_pattern)
+
+    match_count = 0
+    for file_io in file_ios:
+        text = file_io.read()
+
+        _match_count = _grep_text(pattern, text, color)
+
+        print()
+        print(f"Found {_match_count} match for pattern '{raw_pattern}' in {file_io.name}")
+        print()
+
+        match_count += _match_count
+
+    if match_count == 0 or _VERBOSE:
+        pyexpr_regex = regexfmt.pyexpr_regex(pattern.regexp.pattern)
+
+        print(f"# pycalver pattern: '{raw_pattern}'")
+        print("# " + regexfmt.regex101_url(pattern))
+        print(pyexpr_regex)
+        print()
+
+    if match_count == 0:
+        sys.exit(1)
+
+
+@cli.command()
+@click.option(
+    "-v",
+    "--verbose",
+    count=True,
+    help="Control log level. -vv for debug level.",
+)
+@click.argument("pattern")
+@click.argument('files', nargs=-1, type=click.File('r'))
+def grep(
+    pattern: str,
+    files  : typ.Tuple[io.TextIOWrapper],
+    verbose: int = 0,
+) -> None:
+    """Search files for a version pattern."""
+    verbose = max(_VERBOSE, verbose)
+    _configure_logging(verbose)
+
+    raw_pattern = pattern  # use internal naming convention
+
+    isatty = getattr(sys.stdout, 'isatty', lambda: False)
+
+    if isatty():
+        colorama.init()
+        try:
+            _grep(raw_pattern, files, color=True)
+        finally:
+            colorama.deinit()
+    else:
+        _grep(raw_pattern, files, color=False)
+
+
 if __name__ == '__main__':
     cli()