From 76182c27ae8d9f791c9088f0171287443f51aff3 Mon Sep 17 00:00:00 2001
From: Michael Tremer <michael.tremer@ipfire.org>
Date: Fri, 14 Feb 2025 15:55:27 +0000
Subject: [PATCH] log file: Try to process any ANSI escape sequences

This is a rather basic implementation and it has the problem that it
erases the entire timestamp on carriage return, too.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
---
 src/pakfire/log_file.c | 110 +++++++++++++++++++++++++++++++++++++++--
 1 file changed, 105 insertions(+), 5 deletions(-)

diff --git a/src/pakfire/log_file.c b/src/pakfire/log_file.c
index dab4a03e..2733d946 100644
--- a/src/pakfire/log_file.c
+++ b/src/pakfire/log_file.c
@@ -27,6 +27,8 @@
 #include <pakfire/util.h>
 #include <pakfire/xfopen.h>
 
+#define MAX_LINE_LENGTH 4096
+
 struct pakfire_log_file {
 	struct pakfire_ctx* ctx;
 	int nrefs;
@@ -186,7 +188,104 @@ int pakfire_log_file_close(struct pakfire_log_file* self) {
 	return 0;
 }
 
+#define pakfire_log_file_process_line(file, line, buffer) \
+	__pakfire_log_file_process_line(file, line, sizeof(line), buffer)
+
+static int __pakfire_log_file_process_line(struct pakfire_log_file* self,
+		char* line, ssize_t length, const char* p) {
+	char* e = NULL;
+	int num;
+
+	// The cursor position
+	int cursor = 0;
+
+	while (*p) {
+		// Match the beginning of an ESC sequence
+		switch (*p) {
+			case '\x1B':
+				p++;
+
+				// Match CSI sequences
+				switch (*p) {
+					case '[':
+						p++;
+
+						// Parse the number
+						num = strtoul(p, &e, 10);
+
+						// Continue from after the number
+						p = e;
+
+						switch (*p) {
+							// Move the cursor to the left
+							case 'D':
+								cursor -= (num > 0) ? num : 1;
+
+								// Don't go too far left
+								if (cursor < 0)
+									cursor = 0;
+								break;
+
+							// Move the cursor to the right
+							case 'C':
+								cursor += (num > 0) ? num : 1;
+
+								// Don't go too far right
+								if (cursor >= length)
+									cursor = length - 1;
+								break;
+
+							// Move to a certain column
+							case 'G':
+								cursor = (num > 0) ? num - 1 : 0;
+
+								// Don't go too far right
+								if (cursor >= length)
+									cursor = length - 1;
+								break;
+						}
+
+						// Skip the final character
+						p++;
+						break;
+				}
+				break;
+
+			// Backspace
+			case '\x08':
+				if (cursor > 0) {
+					cursor--;
+
+					// Erase the previous character
+					line[cursor] = ' ';
+				}
+				p++;
+				break;
+
+			// Carriage Return
+			case '\x0d':
+				// Erase everything up to the cursor
+				for (int i = 0; i < cursor; i++)
+					line[i] = '\0';
+
+				cursor = 0;
+				p++;
+				break;
+
+			// Normal characters
+			default:
+				if (cursor < length - 1)
+					line[cursor++] = *p;
+				p++;
+				break;
+		}
+	}
+
+	return 0;
+}
+
 int pakfire_log_file_write(struct pakfire_log_file* self, const char* buffer, ssize_t length) {
+	char line[MAX_LINE_LENGTH] = {};
 	int r;
 
 	// Check inputs
@@ -197,13 +296,14 @@ int pakfire_log_file_write(struct pakfire_log_file* self, const char* buffer, ss
 	if (unlikely(!self->f))
 		return -EBADF;
 
-	// Automatically determine the length
-	if (unlikely(length < 0))
-		length = strlen(buffer);
+	// Process any ANSI Escape codes
+	r = pakfire_log_file_process_line(self, line, buffer);
+	if (r < 0)
+		return r;
 
 	// Write the buffer to the file
-	r = fwrite(buffer, 1, length, self->f);
-	if (unlikely(r < length)) {
+	r = fprintf(self->f, "%s", line);
+	if (unlikely(r < 0)) {
 		ERROR(self->ctx, "Could not write to log file: %m\n");
 		return -errno;
 	}
-- 
2.39.5