Added plugin `bracketmatch`

2 files changed, 104 insertions, 0 deletions

diff --git a/README.md b/README.md
index 92bd2e3..2215849 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,7 @@ otherwise the plugin file itself can be submitted.*
 Plugin | Description
 -------|-----------------------------------------
 [`autowrap`](autowrap.lua?raw=1) | Automatically hardwraps lines when typing
+[`bracketmatch`](bracketmatch.lua?raw=1) | [Underlines](https://user-images.githubusercontent.com/3920290/80132745-0c863f00-8594-11ea-8875-c455c6fd7eae.png) matching right-bracket of left-bracket under caret
 [`gofmt`](gofmt.lua?raw=1) | Auto-formats the current go file, adds the missing imports and the missing return cases
 [`indentguide`](indentguide.lua?raw=1) | Adds [indent guides](https://user-images.githubusercontent.com/3920290/79640716-f9860000-818a-11ea-9c3b-26d10dd0e0c0.png)
 [`language_fe`](language_fe.lua?raw=1) | Syntax for the [fe](https://github.com/rxi/fe) programming language
diff --git a/bracketmatch.lua b/bracketmatch.lua
new file mode 100644
index 0000000..b05e8ab
--- /dev/null
+++ b/bracketmatch.lua
@@ -0,0 +1,103 @@
+local core = require "core"
+local style = require "core.style"
+local config = require "core.config"
+local command = require "core.command"
+local keymap = require "core.keymap"
+local DocView = require "core.docview"
+
+local bracket_map = { ["["] = "]", ["("] = ")", ["{"] = "}" }
+
+
+local state = {}
+
+local function update_state(line_limit)
+  line_limit = line_limit or math.huge
+
+  -- reset if we don't have a document (eg. DocView isn't focused)
+  local doc = core.active_view.doc
+  if not doc then
+    state = {}
+    return
+  end
+
+  -- early exit if nothing has changed since the last call
+  local line, col = doc:get_selection()
+  if state.doc == doc and state.line == line and state.col == col
+  and state.limit == line_limit then
+    return
+  end
+
+  -- find matching rbracket if we have an lbracket
+  local line2, col2
+  local chr = doc:get_text(line, col - 1, line, col)
+  local rbracket = bracket_map[chr]
+
+  if rbracket then
+    local ptn = "[%" .. chr .. "%" .. rbracket .. "]"
+    local offset = col - 1
+    local depth = 1
+
+    for i = line, math.min(#doc.lines, line + line_limit) do
+      while offset do
+        local n = doc.lines[i]:find(ptn, offset + 1)
+        if n then
+          local match = doc.lines[i]:sub(n, n)
+          if match == chr then
+            depth = depth + 1
+          elseif match == rbracket then
+            depth = depth - 1
+            if depth == 0 then line2, col2 = i, n end
+          end
+        end
+        offset = n
+      end
+      if line2 then break end
+      offset = 0
+    end
+  end
+
+  -- update
+  state = {
+    doc = doc,
+    line = line,
+    col = col,
+    line2 = line2,
+    col2 = col2,
+    limit = line_limit,
+  }
+end
+
+
+local update = DocView.update
+
+function DocView:update(...)
+  update(self, ...)
+  update_state(100)
+end
+
+
+local draw_line_text = DocView.draw_line_text
+
+function DocView:draw_line_text(idx, x, y)
+  draw_line_text(self, idx, x, y)
+
+  if self.doc == state.doc and idx == state.line2 then
+    local color = style.bracketmatch_color or style.syntax["function"]
+    local x1 = x + self:get_col_x_offset(idx, state.col2)
+    local x2 = x + self:get_col_x_offset(idx, state.col2 + 1)
+    local h = style.divider_size
+    renderer.draw_rect(x1, y + self:get_line_height() - h, x2 - x1, h, color)
+  end
+end
+
+
+command.add("core.docview", {
+  ["bracket-match:move-to-matching"] = function()
+    update_state()
+    if state.line2 then
+      core.active_view.doc:set_selection(state.line2, state.col2)
+    end
+  end,
+})
+
+keymap.add { ["ctrl+m"] = "bracket-match:move-to-matching" }