1 files changed, 160 insertions, 0 deletions
diff --git a/lua/clever_f/host_adapter.lua b/lua/clever_f/host_adapter.lua
index a0eec66..747d9b8 100644
--- a/lua/clever_f/host_adapter.lua
+++ b/lua/clever_f/host_adapter.lua
@@ -41,6 +41,8 @@ function HostAdapter.new(options)
   local adapter = setmetatable({}, HostAdapter)
   adapter_records[adapter] = {
     runtime = require_runtime(current_runtime(options)),
+    next_identity = 1,
+    highlights = {},
   }
   return adapter
 end
@@ -53,6 +55,164 @@ function HostAdapter:runtime()
   return adapter_records[self].runtime
 end
 
+local function next_identity(adapter, prefix)
+  local record = adapter_records[adapter]
+  local identity = prefix .. "-" .. tostring(record.next_identity)
+  record.next_identity = record.next_identity + 1
+  return identity
+end
+
+local function highlight_exists(runtime, name)
+  if type(runtime.fn) == "table" and type(runtime.fn.hlexists) == "function" then
+    return runtime.fn.hlexists(name) == 1
+  end
+  local definition = runtime.api.nvim_get_hl(0, {
+    name = name,
+    link = true,
+    create = false,
+  })
+  return next(definition) ~= nil
+end
+
+function HostAdapter:read_highlight_group(name)
+  if type(name) ~= "string" or name == "" then
+    fail("highlight group name must be a nonempty string", 2)
+  end
+  local runtime = self:runtime()
+  if not highlight_exists(runtime, name) then
+    return nil
+  end
+  return runtime.api.nvim_get_hl(0, {
+    name = name,
+    link = true,
+    create = false,
+  })
+end
+
+local function native_highlight_definition(definition, options)
+  if type(definition) ~= "table" then
+    fail("highlight group definition must be a table", 3)
+  end
+  options = options or {}
+  if type(options) ~= "table" then
+    fail("highlight group options must be a table", 3)
+  end
+  local native = {}
+  for key, value in pairs(definition) do
+    if key ~= "guifg" and key ~= "guibg" and key ~= "gui" then
+      native[key] = value
+    end
+  end
+  if definition.guifg ~= nil then
+    native.fg = definition.guifg
+  end
+  if definition.guibg ~= nil then
+    native.bg = definition.guibg
+  end
+  for key, value in pairs(definition.gui or {}) do
+    native[key] = value
+  end
+  if options.default ~= nil then
+    native.default = options.default
+  end
+  if options.force ~= nil then
+    native.force = options.force
+  end
+  return native
+end
+
+function HostAdapter:define_highlight_group(name, definition, options)
+  if type(name) ~= "string" or name == "" then
+    fail("highlight group name must be a nonempty string", 2)
+  end
+  options = options or {}
+  local runtime = self:runtime()
+  if options.default and highlight_exists(runtime, name) then
+    return false
+  end
+  runtime.api.nvim_set_hl(
+    0,
+    name,
+    native_highlight_definition(definition, options)
+  )
+  return true
+end
+
+local function overlay_positions(specification)
+  local positions = specification.positions
+  if positions == nil and specification.position ~= nil then
+    positions = { specification.position }
+  end
+  if type(positions) ~= "table" then
+    fail("highlight positions must be a list", 3)
+  end
+  local native = {}
+  for index, position in ipairs(positions) do
+    position = domain.Position.coerce(position)
+    native[index] = { position.line, position.byte_column }
+  end
+  if #native == 0 then
+    native[1] = { 0 }
+  end
+  return native
+end
+
+local function overlay_priority(value)
+  if value == "high" then
+    return 100
+  end
+  if value == "ordinary" or value == nil then
+    return 10
+  end
+  if type(value) == "number" then
+    return value
+  end
+  fail("highlight priority must be high, ordinary, or numeric", 3)
+end
+
+function HostAdapter:create_highlight(specification)
+  if type(specification) ~= "table" then
+    fail("highlight specification must be a table", 2)
+  end
+  if type(specification.group) ~= "string" or specification.group == "" then
+    fail("highlight group must be a nonempty string", 2)
+  end
+  if specification.window == nil then
+    fail("highlight window must identify its Nvim window", 2)
+  end
+  local record = adapter_records[self]
+  local identity = specification.identity or next_identity(self, "highlight")
+  if record.highlights[identity] ~= nil then
+    fail("highlight identity is already active", 2)
+  end
+  local match_id = record.runtime.fn.matchaddpos(
+    specification.group,
+    overlay_positions(specification),
+    overlay_priority(specification.priority),
+    -1,
+    { window = specification.window }
+  )
+  if type(match_id) ~= "number" or match_id < 0 then
+    fail("Nvim could not create the window-local highlight", 2)
+  end
+  record.highlights[identity] = {
+    match_id = match_id,
+    window = specification.window,
+  }
+  return identity
+end
+
+function HostAdapter:remove_highlight(identity)
+  local record = adapter_records[self]
+  local resource = record.highlights[identity]
+  if resource == nil then
+    return false
+  end
+  record.highlights[identity] = nil
+  record.runtime.fn.matchdelete(resource.match_id, resource.window)
+  return true
+end
+
 local function escape_key(runtime)
   if type(runtime.keycode) == "function" then
     return runtime.keycode("<Esc>")