From 14f3b8ac56875d2be066a1a93e7ebebb5927023d Mon Sep 17 00:00:00 2001
From: Harry Jeffery <harry@exec64.co.uk>
Date: Mon, 2 Sep 2019 15:39:50 +0100
Subject: console: Implement command history

---
 src/console.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 90 insertions(+), 4 deletions(-)

diff --git a/src/console.c b/src/console.c
index 9243e24..073274f 100644
--- a/src/console.c
+++ b/src/console.c
@@ -1,5 +1,7 @@
 #include "console.h"
 
+#include "list.h"
+
 #include <assert.h>
 #include <ctype.h>
 #include <stdlib.h>
@@ -14,6 +16,10 @@ struct imv_console {
 
   imv_console_callback callback;
   void *callback_data;
+
+  struct list *history;
+  ssize_t history_item; /* -1 when not traversing history */
+  char *history_before; /* contents of line before history was opened */
 };
 
 /* Iterates forwards over characters in a UTF-8 string */
@@ -60,20 +66,88 @@ static size_t prev_char(char *buffer, size_t position)
   return result;
 }
 
+static void add_to_history(struct list *history, const char *line)
+{
+  /* Don't add blank lines */
+  if (line[0] == '\0') {
+    return;
+  }
+
+  /* Don't add the same line consecutively */
+  if (history->len > 0 && !strcmp(history->items[history->len - 1], line)) {
+    return;
+  }
+
+  list_append(history, strdup(line));
+}
+
+static void history_back(struct imv_console *console)
+{
+  if (console->history->len < 1) {
+    /* No history to browse */
+    return;
+  }
+
+  if (console->history_item == 0) {
+    /* At the top of history. Do nothing. */
+    return;
+  }
+
+  if (console->history_item == -1) {
+    /* Enter history from the bottom */
+    free(console->history_before);
+    console->history_before = strdup(console->buffer);
+    console->history_item = console->history->len - 1;
+  } else {
+    /* Move back in history */
+    console->history_item--;
+  }
+
+  strncpy(console->buffer,
+      console->history->items[console->history_item],
+      console->buffer_len);
+  console->cursor = strlen(console->buffer);
+}
+
+static void history_forward(struct imv_console *console)
+{
+  if (console->history_item == -1) {
+    /* Not in history, do nothing */
+    return;
+  }
+
+  if ((size_t)console->history_item == console->history->len - 1) {
+    /* At the end of history, restore the backup */
+    strncpy(console->buffer, console->history_before, console->buffer_len);
+    console->cursor = strlen(console->buffer);
+    free(console->history_before);
+    console->history_before = NULL;
+    console->history_item = -1;
+  } else {
+    /* Move forward in history */
+    console->history_item++;
+    strncpy(console->buffer,
+        console->history->items[console->history_item],
+        console->buffer_len);
+    console->cursor = strlen(console->buffer);
+  }
+
+}
 
 struct imv_console *imv_console_create(void)
 {
   struct imv_console *console = calloc(1, sizeof *console);
   console->buffer_len = 1024;
+  console->history_item = -1;
+  console->history = list_create();
   return console;
 }
 
 void imv_console_free(struct imv_console *console)
 {
-  if (console->buffer) {
-    free(console->buffer);
-    console->buffer = NULL;
-  }
+  free(console->buffer);
+  list_deep_free(console->history);
+  free(console->history_before);
   free(console);
 }
 
@@ -97,6 +171,7 @@ void imv_console_activate(struct imv_console *console)
 
   console->buffer = calloc(1, console->buffer_len);
   console->cursor = 0;
+  console->history_item = -1;
 }
 
 void imv_console_input(struct imv_console *console, const char *text)
@@ -143,6 +218,7 @@ bool imv_console_key(struct imv_console *console, const char *key)
     if (console->callback) {
       console->callback(console->buffer, console->callback_data);
     }
+    add_to_history(console->history, console->buffer);
     free(console->buffer);
     console->buffer = NULL;
     return true;
@@ -158,6 +234,16 @@ bool imv_console_key(struct imv_console *console, const char *key)
     return true;
   }
 
+  if (!strcmp("Up", key) || !strcmp("Ctrl+p", key)) {
+    history_back(console);
+    return true;
+  }
+
+  if (!strcmp("Down", key) || !strcmp("Ctrl+n", key)) {
+    history_forward(console);
+    return true;
+  }
+
   if (!strcmp("Ctrl+a", key)) {
     console->cursor = 0;
     return true;
-- 
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