feat(test): test panel

lua/cp/diff.lua

@@ -0,0 +1,150 @@
+---@class DiffResult
+---@field content string[]
+---@field highlights table[]?
+
+---@class DiffBackend
+---@field name string
+---@field render fun(expected: string, actual: string, mode: string?): DiffResult
+
+local M = {}
+
+---Vim's built-in diff backend using diffthis
+---@type DiffBackend
+local vim_backend = {
+  name = 'vim',
+  render = function(expected, actual, mode)
+    -- For vim backend, we return the content as-is since diffthis handles highlighting
+    local expected_lines = vim.split(expected, '\n', { plain = true, trimempty = true })
+    local actual_lines = vim.split(actual, '\n', { plain = true, trimempty = true })
+
+    return {
+      content = actual_lines,
+      highlights = nil -- diffthis handles highlighting
+    }
+  end
+}
+
+---Git word-diff backend for character-level precision
+---@type DiffBackend
+local git_backend = {
+  name = 'git',
+  render = function(expected, actual, mode)
+    -- Create temporary files for git diff
+    local tmp_expected = vim.fn.tempname()
+    local tmp_actual = vim.fn.tempname()
+
+    vim.fn.writefile(vim.split(expected, '\n', { plain = true }), tmp_expected)
+    vim.fn.writefile(vim.split(actual, '\n', { plain = true }), tmp_actual)
+
+    local cmd = {
+      'git', 'diff', '--no-index', '--word-diff=plain', '--word-diff-regex=.',
+      '--no-prefix', tmp_expected, tmp_actual
+    }
+
+    local result = vim.system(cmd, { text = true }):wait()
+
+    -- Clean up temp files
+    vim.fn.delete(tmp_expected)
+    vim.fn.delete(tmp_actual)
+
+    if result.code == 0 then
+      -- No differences, return actual content as-is
+      return {
+        content = vim.split(actual, '\n', { plain = true, trimempty = true }),
+        highlights = {}
+      }
+    else
+      -- Parse git diff output
+      local lines = vim.split(result.stdout or '', '\n', { plain = true })
+      local content_lines = {}
+      local highlights = {}
+
+      -- Skip git diff header lines (start with @@, +++, ---, etc.)
+      local content_started = false
+      for _, line in ipairs(lines) do
+        if content_started or (not line:match('^@@') and not line:match('^%+%+%+') and not line:match('^%-%-%-') and not line:match('^index')) then
+          content_started = true
+          if line:match('^[^%-+]') or line:match('^%+') then
+            -- Skip lines starting with - (removed lines) for the actual pane
+            -- Only show lines that are unchanged or added
+            if not line:match('^%-') then
+              local clean_line = line:gsub('^%+', '') -- Remove + prefix
+              table.insert(content_lines, clean_line)
+
+              -- Parse highlights will be handled in highlight.lua
+              table.insert(highlights, {
+                line = #content_lines,
+                content = clean_line
+              })
+            end
+          end
+        end
+      end
+
+      return {
+        content = content_lines,
+        highlights = highlights
+      }
+    end
+  end
+}
+
+---Available diff backends
+---@type table<string, DiffBackend>
+local backends = {
+  vim = vim_backend,
+  git = git_backend,
+}
+
+---Get available backend names
+---@return string[]
+function M.get_available_backends()
+  return vim.tbl_keys(backends)
+end
+
+---Get a diff backend by name
+---@param name string
+---@return DiffBackend?
+function M.get_backend(name)
+  return backends[name]
+end
+
+---Check if git backend is available
+---@return boolean
+function M.is_git_available()
+  local result = vim.system({'git', '--version'}, { text = true }):wait()
+  return result.code == 0
+end
+
+---Get the best available backend based on config and system availability
+---@param preferred_backend? string
+---@return DiffBackend
+function M.get_best_backend(preferred_backend)
+  if preferred_backend and backends[preferred_backend] then
+    if preferred_backend == 'git' and not M.is_git_available() then
+      -- Fall back to vim if git is not available
+      return backends.vim
+    end
+    return backends[preferred_backend]
+  end
+
+  -- Default to git if available, otherwise vim
+  if M.is_git_available() then
+    return backends.git
+  else
+    return backends.vim
+  end
+end
+
+---Render diff using specified backend
+---@param expected string
+---@param actual string
+---@param backend_name? string
+---@param mode? string
+---@return DiffResult
+function M.render_diff(expected, actual, backend_name, mode)
+  local backend = M.get_best_backend(backend_name)
+  return backend.render(expected, actual, mode)
+end
+
+return M