From 2a82f0149318c520591c67512a2fdc2a3864065e Mon Sep 17 00:00:00 2001
From: Robbe Van Herck <robbevanherck1@gmail.com>
Date: Thu, 9 Jan 2020 18:32:12 +0100
Subject: [PATCH] Add minimal shell, find out that stuff is broken :'(

---
 README.md         |   4 +-
 kernel/kernel.c   |   4 +-
 kernel/shell.c    | 111 ++++++++++++++++++++++++++++++++++++++++++++++
 kernel/terminal.c |   1 +
 4 files changed, 117 insertions(+), 3 deletions(-)
 create mode 100644 kernel/shell.c

diff --git a/README.md b/README.md
index acd52fa..f6d55a0 100644
--- a/README.md
+++ b/README.md
@@ -26,10 +26,11 @@ The kernel is based on [the bare bones kernel from the OSDev wiki](https://wiki.
 ### Features
 
 - [x] Terminal output (with newlines!)
-- [x] _Very_ basic memory management
+- [x] _Very_ basic (and probably broken) memory management
 - [x] Interrupt handling
 - [x] Keyboard input
 - [x] Exception handling
+- [x] Minimal shell
 - [ ] Filesystem interaction
   - [ ] Show files in directory
   - [ ] Read files in directory
@@ -37,5 +38,6 @@ The kernel is based on [the bare bones kernel from the OSDev wiki](https://wiki.
 - [ ] Tests
 - [ ] Running executables from filesystem
 - [ ] Better memory management
+- [ ] Better shell
 
 As a test, I've implemented day 1 of [advent of code](https://adventofcode.com/) on the [AoC branch](https://github.com/Robbe7730/RoBoot/tree/AoC).
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 60f50db..7fa4427 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -15,6 +15,7 @@
 #include "terminal.c"
 #include "memory.c"
 #include "interrupts.c"
+#include "shell.c"
 
 static inline bool are_interrupts_enabled() {
     unsigned long flags;
@@ -61,7 +62,6 @@ void kernel_main(void)
 	interrupt_init();
 
 	for(;;) {
-		char curr_char = getchar();
-		terminal_putchar(curr_char);
+		shell_step();
 	}
 }
\ No newline at end of file
diff --git a/kernel/shell.c b/kernel/shell.c
new file mode 100644
index 0000000..a404a8c
--- /dev/null
+++ b/kernel/shell.c
@@ -0,0 +1,111 @@
+#ifndef SHELL_C
+#define SHELL_C
+
+#define SHELL_CMD_BUFFER_SIZE 128
+
+#include <stddef.h>
+
+#include "terminal.c"
+#include "drivers/keyboard/keyboard.c"
+
+char buffer[SHELL_CMD_BUFFER_SIZE];
+int buffer_idx = 0;
+
+int echo(char* input) {
+    terminal_writestring(input);
+    terminal_putchar('\n');
+    return 0;
+}
+
+int hello(char* unused) {
+    terminal_writestring("Hello, world!\n");
+    return 0;
+}
+
+int cls(char* unused) {
+    terminal_initialize();
+    return 0;
+}
+
+int ree(char* unused) {
+    terminal_initialize();
+    terminal_putchar('R');
+    for (int i = 1; i < VGA_WIDTH * VGA_HEIGHT; i++) {
+        terminal_putchar('e');
+    }
+    return 0;
+}
+
+int run_command(char* buffer) {
+    // TODO If I make these 2 global, it breaks...
+    // TODO This is ugly, fix this 
+    const char* shell_commands_strings[] = {
+        "echo",
+        "hello",
+        "cls",
+        "ree",
+        NULL
+    };
+
+    int (*shell_commands_functions[]) (char*) = {
+        echo,
+        hello,
+        cls,
+        ree
+    };
+
+    if(buffer[0] == 0) {
+        return 0;
+    }
+    char command[SHELL_CMD_BUFFER_SIZE] = {0};
+    int i = 0;
+    while (buffer[i] != 0 && buffer[i] != ' ') {
+        command[i] = buffer[i];
+        i++;
+    }
+
+    int command_idx = 0;
+
+    while(shell_commands_strings[command_idx] != NULL) {
+        int check_idx = 0;
+        while(command[check_idx] != 0 && shell_commands_strings[command_idx][check_idx] == command[check_idx]) {
+            check_idx++;
+        }
+        if (command[check_idx] == 0 && shell_commands_strings[command_idx][check_idx] == 0) {
+            return (shell_commands_functions[command_idx])(buffer + i + 1);
+        }
+        command_idx++;
+    }
+    return -1;
+}
+
+void shell_step() {
+    char curr_char = getchar();
+
+
+    if (curr_char == '\n') {
+        terminal_putchar(curr_char);
+        buffer[buffer_idx] = 0;
+        int result = run_command(buffer);
+        for (int i = 0; i < SHELL_CMD_BUFFER_SIZE; i++) {
+            buffer[i] = 0;
+        }
+        buffer_idx = 0;
+
+        if (result == -1) {
+            terminal_writestring("No such command\n");
+        }
+    } else if (curr_char == 0x08) {
+        if (buffer_idx != 0) {
+            buffer_idx--;
+            buffer[buffer_idx] = 0;
+            terminal_putchar(curr_char);
+        }
+    } else {
+        buffer[buffer_idx] = curr_char;
+        buffer_idx++;
+        terminal_putchar(curr_char);
+    }
+}
+
+#endif //SHELL_C
\ No newline at end of file
diff --git a/kernel/terminal.c b/kernel/terminal.c
index 40e51e3..5b9698a 100644
--- a/kernel/terminal.c
+++ b/kernel/terminal.c
@@ -77,6 +77,7 @@ void terminal_putchar(char c) {
 		return;
 	}
 	if (c == 0x08) {
+		terminal_putentryat(' ', terminal_color, terminal_column, terminal_row);
 		if (terminal_column == 0) {
 			if(terminal_row != 0) {
 				terminal_row--;