From c8b4d93c89bc8f5713bc23424ccd3dba0170782a Mon Sep 17 00:00:00 2001
From: lisk77 <lisk77@protonmail.com>
Date: Mon, 18 Aug 2025 16:34:56 +0200
Subject: [PATCH] feat(cli): added the diff command to display the difference
 of two files

---
 include/utilities.h | 22 ++++++++++++++++
 src/main.c          | 62 +++++++++++++++++++++++++++++++++++++++------
 2 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/include/utilities.h b/include/utilities.h
index 593859b..08b5a0d 100644
--- a/include/utilities.h
+++ b/include/utilities.h
@@ -1,6 +1,9 @@
 #ifndef UTILITIES_H
 #define UTILITIES_H
 
+#include <sys/stat.h>
+#include <errno.h>
+
 #include "file.h"
 #include "action_list.h"
 
@@ -9,6 +12,25 @@
 #define GREEN_BG "\033[42m"
 #define BLACK_FG "\033[30m"
 
+typedef enum {
+    PT_NOEXIST,
+    PT_FILE,
+    PT_DIR,
+    PT_OTHER,
+    PT_ERROR
+} PathType;
+
+PathType get_path_type(const char* path) {
+    struct stat st;
+    int rc = stat(path, &st);
+    if (rc != 0) {
+        return (errno == ENOENT) ? PT_NOEXIST : PT_ERROR;
+    }
+    if (S_ISREG(st.st_mode))  return PT_FILE;
+    if (S_ISDIR(st.st_mode))  return PT_DIR;
+    return PT_OTHER;
+}
+
 void visualize_diff(File* old_version, File* new_version, ActionList* actions) {
     int* deleted_lines = calloc(old_version->lines, sizeof(int));
     int* inserted_lines = calloc(new_version->lines, sizeof(int));
diff --git a/src/main.c b/src/main.c
index b6b20b6..2483906 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,16 +1,62 @@
 #include "action_list.h"
+#include "file.h"
+#include "myers.h"
+#include "utilities.h"
+// main.c
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
 
-int main() {
-    Action act1 = (Action){.type=INSERT, .line_original=0, .line_changed=1};
-    Action act2 = (Action){.type=DELETE, .line_original=1, .line_changed=2};
+static void usage(int exitcode) {
+    printf("usage: merk <command> [<args>]\n\n  diff     Displays the difference between the given two files\n");
+    exit(exitcode);
+}
 
-    ActionList* list1 = new_list();
-    add_action(list1, act1);
+int main(int argc, char **argv) {
+    if (argc == 2 && (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help"))) {
+        usage(0);
+    }
 
-    ActionList* list2 = new_list();
-    add_action(list2, act2);
+    const char* subcmd = argv[1];
 
-    append_list(list1, list2);
+    if (strcmp(subcmd, "diff") != 0) {
+        fprintf(stderr, "ERROR: Unknown subcommand: '%s'\n", subcmd);
+        usage(2);
+    }
+
+    if (strcmp(subcmd, "diff") == 0) {
+        if (argc != 4) {
+            printf("ERROR: too many/too little arguments given!\n");
+            printf("Usage: merk diff <PATH> <PATH>");
+            exit(1);
+        }
+
+        File* file1; 
+        switch (get_path_type(argv[2])) {
+            case PT_FILE: file1 = new_file(argv[2]); break;
+            case PT_DIR: file1 = NULL; printf("ERROR: first path is a directory and no file!"); break;
+            case PT_NOEXIST: file1 = NULL; printf("ERROR: first path does not exist!"); break;
+            default: file1 = NULL; printf("ERROR: unknown first path!");
+        }
+        if (!file1) exit(1);
+        File* file2;
+        switch (get_path_type(argv[3])) {
+            case PT_FILE: file2 = new_file(argv[3]); break;
+            case PT_DIR: file2 = NULL; printf("ERROR: second path is a directory and no file!"); break;
+            case PT_NOEXIST: file2 = NULL; printf("ERROR: second path does not exist!"); break;
+            default: file2 = NULL; printf("ERROR: unknown second path!");
+        }
+        if (!file2) exit(1);
+
+        ActionList* actions = myers_diff(file1, file2, 0, 0);
+        if (!actions) printf("ERROR: something went wrong while taking the diff!");
+        else visualize_diff(file1, file2, actions);
+    }
+    else {
+        usage(1);
+    }
 
     return 0;
 }
+