Update grep

Author: Abhijit Sarkar

grep/grep.py

@@ -1,52 +1,52 @@
 import re
 
-import grep_test as gt  # type: ignore[import-not-found]
-
 
 def grep(pattern: str, flags: str, files: list[str]) -> str:
     filename = len(files) > 1
     line_numbers = "-n" in flags
     name_only = "-l" in flags
 
-    pattern_txt = __build_pattern(flags).replace("{}", pattern)
+    pattern_txt = _build_pattern(pattern, flags)
     p = re.compile(rf"{pattern_txt}")
-    result = []
+    result: list[str] = []
 
     for f in files:
-        lines = gt.FILE_TEXT[f].splitlines()
-        for line_num, line in enumerate(lines):
-            if not re.search(p, line):
-                continue
-            if name_only:
-                result.append(f)
-                break
-            temp = []
-            if filename:
-                temp.append(f"{f}:")
-            if line_numbers:
-                temp.append(f"{line_num + 1}:")
-            temp.append(line)
-            result.append("".join(temp))
+        with open(f, encoding="UTF-8") as file:
+            line_num = -1
+            while line := file.readline().rstrip("\n"):
+                line_num += 1
+                if not re.search(p, line):
+                    continue
+                if name_only:
+                    result.append(f)
+                    break
+                temp = []
+                if filename:
+                    temp.append(f"{f}:")
+                if line_numbers:
+                    temp.append(f"{line_num + 1}:")
+                temp.append(line)
+                result.append("".join(temp))
 
     return ("\n".join(result) + "\n") if result else ""
 
 
-def __build_pattern(flags: str) -> str:
+def _build_pattern(pattern: str, flags: str) -> str:
     case_insensitive = "-i" in flags
     invert = "-v" in flags
     whole_line = invert or "-x" in flags
 
-    xs = []
+    xs: list[str] = []
     if case_insensitive:
         xs.append("(?i)")
     if whole_line:
         xs.append("^")
     if invert:
         # Negative lookahead.
         # https://www.regular-expressions.info/lookaround.html
-        xs.append("(?:(?!{}).)*")
+        xs.append(f"(?:(?!{pattern}).)*")
     else:
-        xs.append("(?:{})")
+        xs.append(f"(?:{pattern})")
     if whole_line:
         xs.append("$")