feat: initial release

lua/tiny-spark/init.lua

@@ -0,0 +1,92 @@
+local M = {}
+
+function M.setup(opts)
+  opts = opts or {}
+  local threshold = opts.threshold or 3
+  local duration = opts.duration or 50
+  local step = math.ceil(1000 / 60)
+  local prev = { 0, 0 }
+  local ns = vim.api.nvim_create_namespace("tiny-spark")
+
+  local trail_chars = opts.chars or { "░", "▒", "▓", "█" }
+  local palette = opts.palette
+    or {
+      { fg = "#552200" },
+      { fg = "#cc4400" },
+      { fg = "#ff8822" },
+      { fg = "#ffcc44" },
+      { fg = "#ffffff", bold = true },
+    }
+  for i, def in ipairs(palette) do
+    vim.api.nvim_set_hl(0, "TinySpark" .. i, def)
+  end
+
+  vim.api.nvim_create_autocmd("CursorMoved", {
+    group = vim.api.nvim_create_augroup("tiny-spark", { clear = true }),
+    callback = function()
+      local cur = vim.api.nvim_win_get_cursor(0)
+      local dy = cur[1] - prev[1]
+      local dx = cur[2] - prev[2]
+      local dist = math.abs(dy)
+      local old_prev = { prev[1], prev[2] }
+      prev = cur
+      if dist < threshold then
+        return
+      end
+
+      local buf = vim.api.nvim_get_current_buf()
+      local line_count = vim.api.nvim_buf_line_count(buf)
+      local dir = dy > 0 and 1 or -1
+
+      -- Build trail from origin to destination
+      local trail = {}
+      for i = 0, dist - 1 do
+        local t = dist > 1 and i / (dist - 1) or 1
+        local row = old_prev[1] - 1 + dir * i
+        local col = old_prev[2] + math.floor(dx * t + 0.5)
+        if row >= 0 and row < line_count and col >= 0 then
+          table.insert(trail, { row = row, col = col })
+        end
+      end
+
+      local elapsed = 0
+      local timer = vim.uv.new_timer()
+      timer:start(
+        0,
+        step,
+        vim.schedule_wrap(function()
+          elapsed = elapsed + step
+          vim.api.nvim_buf_clear_namespace(buf, ns, 0, -1)
+
+          if elapsed >= duration or not vim.api.nvim_buf_is_valid(buf) or #trail == 0 then
+            timer:stop()
+            if not timer:is_closing() then
+              timer:close()
+            end
+            return
+          end
+
+          -- Shrink trail from origin end (remove the dark/far end first)
+          local progress = elapsed / duration
+          local drop = math.floor(#trail * progress)
+          local start = drop + 1
+
+          for i = start, #trail do
+            local p = trail[i]
+            -- t=0 at start of visible trail (dimmest), t=1 at destination (brightest)
+            local t = (#trail - start) > 0 and (i - start) / (#trail - start) or 1
+            local char_idx = math.max(1, math.min(#trail_chars, math.ceil(t * #trail_chars)))
+            local hl_idx = math.max(1, math.min(#palette, math.ceil(t * #palette)))
+            pcall(vim.api.nvim_buf_set_extmark, buf, ns, p.row, 0, {
+              virt_text = { { trail_chars[char_idx], "TinySpark" .. hl_idx } },
+              virt_text_pos = "overlay",
+              virt_text_win_col = p.col,
+            })
+          end
+        end)
+      )
+    end,
+  })
+end
+
+return M