input: Implement console input handling and add shell for real this time

Self explanatory, we finally have a working ish shell

Now we need to do some more stuff or something, probably work on a fork or something

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

Co-authored-by: Copilot <copilot@github.com>

user/programs/init.c

@@ -1,6 +1,7 @@
 #include "../include/syscalls.h"
 
-#define STDOUT 1
+#define STDIN    0
+#define STDOUT  1
 
 unsigned strlen(const char* str)
 {
@@ -13,6 +14,64 @@ unsigned strlen(const char* str)
     return len;
 }
 
+static int strcmp(const char* a, const char* b)
+{
+    while (*a && (*a == *b)) {
+        a++;
+        b++;
+    }
+    return *(unsigned char*)a - *(unsigned char*)b;
+}
+
+static void print(const char* s)
+{
+    syscall(SYS_WRITE, STDOUT, (unsigned long)s, strlen(s), 0, 0, 0);
+}
+
+static void readline(char* buf, unsigned long max)
+{
+    unsigned long i = 0;
+
+    while (i < max - 1)
+    {
+        char c;
+        long n = syscall(SYS_READ, STDIN, (unsigned long)&c, 1, 0, 0, 0);
+
+        if (n <= 0)
+            continue;
+
+        if (c == '\n')
+            break;
+
+        if (c == '\b') {
+            if (i > 0) i--;
+            continue;
+        }
+
+        buf[i++] = c;
+    }
+
+    buf[i] = '\0';
+}
+
+static void cat(const char* path)
+{
+    unsigned char buf[256];
+
+    long fd = syscall(SYS_OPEN, (unsigned long)path, 0, 0, 0, 0, 0);
+    if (fd < 0) {
+        print("cat: cannot open file\n");
+        return;
+    }
+
+    long n = syscall(SYS_READ, fd, (unsigned long)buf, sizeof(buf), 0, 0, 0);
+    syscall(SYS_CLOSE, fd, 0, 0, 0, 0, 0);
+
+    if (n > 0)
+        syscall(SYS_WRITE, STDOUT, (unsigned long)buf, n, 0, 0, 0);
+}
+
+
 void main()
 {
     const unsigned char* path = "/qwerty.txt";
@@ -41,6 +100,30 @@ void main()
     // ── print buffer to stdout ───────────────
     syscall(SYS_WRITE, STDOUT, (unsigned long)buf, n, 0, 0, 0);
 
+    char line[128];
+
+    while (1)
+    {
+        print("> ");
+
+        readline(line, sizeof(line));
+
+        if (strcmp(line, "exit") == 0)
+            break;
+
+        // simple "cat <path>"
+        if (line[0] == 'c' && line[1] == 'a' && line[2] == 't' && line[3] == ' ')
+        {
+            cat(&line[4]);
+            continue;
+        }
+
+        if (line[0] != '\0')
+            print("Unknown command\n");
+    }
+
+    while (1);
+
     // ── done ────────────────────────────────
     while (1);
 }