feat: line editor

Makefile

@@ -9,11 +9,11 @@ ifeq ($(RELEASE),true)
 	CFLAGS += -O3
 endif
 
-.PHONY: clean
+.PHONY: clean release-$(RELEASE)
 
 all: dist/msh
 
-dist/msh: $(SOURCES) dist
+dist/msh: $(SOURCES) dist release-$(RELEASE)
 	$(CC) -o $@ $(SOURCES) $(CFLAGS)
 
 dist:

src/msh.c

@@ -7,6 +7,7 @@
 #include <sys/wait.h>
 #include <sys/utsname.h>
 #include <errno.h>
+#include <termios.h>
 
 
 #define ESC \x1B
@@ -35,13 +36,112 @@ void pretty_path_home(char** path) {
 }
 
 
+#define ANSI_UNKNOWN             -1
+#define ANSI_CURSOR_LEFT         0
+#define ANSI_CURSOR_RIGHT        1
+#define ANSI_CURSOR_UP           2
+#define ANSI_CURSOR_DOWN         3
+#define ANSI_DELETE_WORD         4
+#define ANSI_CURSOR_LEFT_WORD    5
+#define ANSI_CURSOR_RIGHT_WORD   6
+#define ANSI_CURSOR_UP_WORD      7
+#define ANSI_CURSOR_DOWN_WORD    8
+
+
+int read_ansi() {
+    switch (getchar()) {
+        case '[':
+            switch(getchar()) {
+                case 'A':
+                    return ANSI_CURSOR_UP;
+                case 'B':
+                    return ANSI_CURSOR_DOWN;
+                case 'C':
+                    return ANSI_CURSOR_RIGHT;
+                case 'D':
+                    return ANSI_CURSOR_LEFT;
+                case '1':
+                    switch(getchar()) {
+                        case ';':
+                            switch(getchar()) {
+                                // CTRL
+                                case '5':
+                                // ALT
+                                case '3':
+                                    switch (getchar()) {
+                                        case 'C':
+                                            return ANSI_CURSOR_RIGHT_WORD;
+                                        case 'D':
+                                            return ANSI_CURSOR_LEFT_WORD;
+                                    }
+                                    break;
+                            }
+                            break;
+                    }
+                    break;
+            }
+            break;
+        case 127:
+        case 8:
+            return ANSI_DELETE_WORD;
+        default:
+            return ANSI_UNKNOWN;
+    }
+
+    return ANSI_UNKNOWN;
+}
+
+
+// Find the length of the prefix until the last occurrence of a rejected character
+size_t strnrcspn(char* str, size_t n, char* reject) {
+    size_t i;
+    int seenaccept = 0;
+
+    for (i = n - 1; i > 0; i--) {
+        // If this is NOT a reject character
+        if(strchr(reject, str[i]) == NULL) {
+            seenaccept = 1;
+            continue;
+        } else {
+            if (seenaccept == 1) {
+                break;
+            }
+        }
+    }
+
+    return i;
+}
+
+// Find the length of the prefix until the first occurrence of a rejected character after an offset
+size_t strnocspn(char* str, size_t n, size_t o, char* reject) {
+    size_t i;
+    int seenaccept = 0;
+
+    for (i = o; i < n; i++) {
+        // If this is NOT a reject character
+        if(strchr(reject, str[i]) == NULL) {
+            seenaccept = 1;
+            continue;
+        } else {
+            if (seenaccept == 1) {
+                break;
+            }
+        }
+    }
+
+    return i;
+}
+
+
 int main(int argc, char** argv) {
+    int retval = 0;
     char*   tokens[LINESIZE] = {};
     char**  args;
     char    line[LINESIZE] = {};
+    char    prompt[LINESIZE] = {};
+    int     linelen = 0;
     char*   tokenwork;
     char*   token;
-    char* newline;
     int     ntokens = 0;
 
     int i;
@@ -63,15 +163,27 @@ int main(int argc, char** argv) {
     int result = uname(&uts);
     if (result != 0) {
         fprintf(stderr, "Error: %s\n", strerror(errno));
-        return errno;
+        retval = errno;
+        goto cleanup;
     }
 
     host = uts.nodename;
 
+
+    struct termios term, orig_term;
+    tcgetattr(fileno(stdin), &term);
+    orig_term = term;
+
+    // disable echo and icanon (don't wait for newline)
+    term.c_lflag &= ~(ECHO | ICANON);
+
+
+    // Main loop
     while(1) {
         char* result = getcwd(pwd, LINESIZE - 1);
         if (result == NULL) {
-            return 1;
+            retval = 1;
+            goto cleanup;
         }
 
         pwd_disp = pwd;
@@ -81,19 +193,95 @@ int main(int argc, char** argv) {
         if (laststatus != 0) {
             fprintf(stdout, "❌");
         }
-        fprintf(stdout, "%s@%s %s$ ", user, host, pwd_disp);
+        snprintf(prompt, LINESIZE, "%s@%s %s$ ", user, host, pwd_disp);
-        char* fgets_res = fgets(line, LINESIZE, stdin);
+        printf("%s", prompt);
 
-        if (fgets_res == NULL) {
+
+        // prepare for input
+        linelen = 0;
+        int readc;
+        int cursor = 0;
+
+        tcsetattr(fileno(stdin), 0, &term);
+
+        memset(line, 0, LINESIZE);
+
+        while ((readc = getchar()) != '\n') {
+            if (readc == EOF) {
                 printf("^D\n");
-            return 0;
+                retval = 0;
+                goto cleanup;
             }
 
-        newline = strrchr(line, '\n');
+            if (readc == '\x1b') {
-        if (newline != NULL) {
+                int ansi = read_ansi();
-            newline[0] = 0;
+                if (ansi == ANSI_CURSOR_LEFT) {
+                    if (cursor > 0) {
+                        cursor--;
+                    }
+                } else if (ansi == ANSI_CURSOR_RIGHT) {
+                    if (cursor < linelen) {
+                        cursor++;
+                    }
+                } else if (ansi == ANSI_DELETE_WORD) {
+                    if (cursor > 0) {
+                        size_t index = strnrcspn(line, cursor, " \t");
+                        memmove(line + index, line + cursor, LINESIZE - cursor);
+                        linelen -= cursor - index;
+                        cursor = index;
+                    }
+                } else if (ansi == ANSI_CURSOR_LEFT_WORD) {
+                    size_t index = strnrcspn(line, cursor, " \t");
+                    cursor = index;
+                } else if (ansi == ANSI_CURSOR_RIGHT_WORD) {
+                    size_t index = strnocspn(line, linelen, cursor, " \t");
+                    cursor = index;
                 }
 
+                goto print_prompt;
+            }
+
+            // backspace
+            if (readc == 127) {
+                if (cursor > 0) {
+                    cursor--;
+                    linelen--;
+                }
+
+                if (cursor == linelen) {
+                    line[cursor] = 0;
+                } else {
+                    memmove(line + cursor, line + cursor + 1, LINESIZE - (cursor));
+                }
+
+                // We don't want to change the line
+                goto print_prompt;
+            }
+
+            if (cursor != linelen) {
+                memmove(line + cursor + 1, line + cursor, LINESIZE - cursor - 1);
+            }
+
+            line[cursor] = readc;
+            cursor++;
+            linelen++;
+
+print_prompt:
+            // Manual echo
+            printf("\x1b[2K\x1b[0G%s%s", prompt, line);
+            for (int j = 0; j < linelen - cursor; j++) {
+                printf("\x1b[D");
+            }
+            fflush(stdout);
+        }
+
+        putc('\n', stdout);
+
+        tcsetattr(fileno(stdin), 0, &orig_term);
+
+        line[linelen] = 0;
+        
+        // Split into tokens
         for (tokenwork = line, i = 0; ; tokenwork = NULL, i++) {
             token = strtok(tokenwork, " \t");
             if (token == NULL) {
@@ -114,7 +302,8 @@ int main(int argc, char** argv) {
         // Shell builtins
         if (strcmp("exit", tokens[0]) == 0) {
             printf("Goodbye!\n");
-            return 0;
+            retval = 0;
+            goto cleanup;
         }
 
         if (strcmp("cd", tokens[0]) == 0) {
@@ -134,5 +323,10 @@ int main(int argc, char** argv) {
         }
 
     }
+
+
+cleanup:
+    tcsetattr(fileno(stdin), 0, &orig_term);
+    return retval;
 }