From 1786b9fea2a94924fe46c61c67811fdc919e0a0a Mon Sep 17 00:00:00 2001
From: Uko Kokņevičs
Date: Wed, 21 Feb 2024 23:00:48 +0200
Subject: Add functionality for skipping paragraphs up and down

---
 src/Buffer.zig    | 32 ++++++++++++++++++++++++++++++++
 src/KeyMap.zig    |  6 ++++++
 src/KeyReader.zig |  8 +++++---
 3 files changed, 43 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/Buffer.zig b/src/Buffer.zig
index f9a1576..bb6d3ce 100644
--- a/src/Buffer.zig
+++ b/src/Buffer.zig
@@ -94,6 +94,22 @@ pub fn backwardDeleteChar(self: *Buffer) !void {
     return self.deleteChar();
 }
 
+pub fn backwardParagraph(self: *Buffer) void {
+    if (self.cy == 0) {
+        return;
+    }
+
+    self.cy -= 1;
+    while (self.cy > 0) : (self.cy -= 1) {
+        // TODO: I'm lazy but also consider lines of only whitespace
+        if (self.rows.items[self.cy].data.items.len == 0) {
+            break;
+        }
+    }
+
+    self.cx = 0;
+}
+
 pub fn cleanWhiteSpace(self: *Buffer) !void {
     for (self.rows.items) |*row| {
         try row.cleanWhiteSpace(self);
@@ -272,6 +288,22 @@ pub fn forwardChar(self: *Buffer) void {
     }
 }
 
+pub fn forwardParagraph(self: *Buffer) void {
+    if (self.cy == self.rows.items.len) {
+        return;
+    }
+
+    self.cy += 1;
+    while (self.cy < self.rows.items.len) : (self.cy += 1) {
+        // TODO: I'm lazy but also consider whitespace-only lines
+        if (self.rows.items[self.cy].data.items.len == 0) {
+            break;
+        }
+    }
+
+    self.cx = 0;
+}
+
 // TODO: Make use of the callback feature to go to the final line while typing in.
 pub fn goToLine(self: *Buffer, editor: *Editor) !void {
     if (try editor.prompt(self.allocator, "Goto line")) |line_str| {
diff --git a/src/KeyMap.zig b/src/KeyMap.zig
index 8df4c06..90dcd01 100644
--- a/src/KeyMap.zig
+++ b/src/KeyMap.zig
@@ -112,11 +112,17 @@ pub fn defaultMap(allocator: Allocator) !KeyMap {
     try map.bind(&.{Key.meta(Key.ctrl('d'))}, Buffer.backwardDeleteChar);
 
     // M-<*>
+    try map.bind(&.{Key.meta(Key.down)}, Buffer.forwardParagraph);
+    try map.bind(&.{Key.meta(Key.up)}, Buffer.backwardParagraph);
     // M-g is taken
+    try map.bind(&.{Key.meta('n')}, Buffer.forwardParagraph);
     // M-O is taken
+    try map.bind(&.{Key.meta('p')}, Buffer.backwardParagraph);
     try map.bind(&.{Key.meta('v')}, Buffer.pageUp);
 
     // C-<*>
+    try map.bind(&.{Key.ctrl(Key.down)}, Buffer.forwardParagraph);
+    try map.bind(&.{Key.ctrl(Key.up)}, Buffer.backwardParagraph);
     try map.bind(&.{Key.ctrl('a')}, Buffer.moveBeginningOfLine);
     try map.bind(&.{Key.ctrl('b')}, Buffer.backwardChar);
     try map.bind(&.{Key.ctrl('d')}, Buffer.deleteChar);
diff --git a/src/KeyReader.zig b/src/KeyReader.zig
index 28e6dcb..5ddef82 100644
--- a/src/KeyReader.zig
+++ b/src/KeyReader.zig
@@ -31,7 +31,7 @@ pub fn readKey(self: *KeyReader) Error!Key {
     const reader = std.io.getStdIn().reader();
     const char = try readByteBlocking(reader);
     if (char == '\x1b') {
-        return self.readMetaKey(reader);
+        return self.readMetaKey(reader, true);
     } else if (char == '\x9b') {
         return self.readControlSequence(reader);
     } else {
@@ -186,9 +186,11 @@ fn readControlSequence(self: *KeyReader, reader: File.Reader) !Key {
     return Key.meta('[');
 }
 
-fn readMetaKey(self: *KeyReader, reader: File.Reader) Error!Key {
+fn readMetaKey(self: *KeyReader, reader: File.Reader, canRecurse: bool) Error!Key {
     if (try readByte(reader)) |char| {
-        if (char == '[') {
+        if (char == '\x1b' and canRecurse) {
+            return Key.meta(try self.readMetaKey(reader, false));
+        } else if (char == '[') {
             return self.readControlSequence(reader);
         } else {
             return Key.meta(char);
-- 
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