refactor: select_character.lua (#647)

将获取按键移动到 init 函数
简化了中文取字方法
预先判断无候选（加入了 alphabet 但无候选词）防止 error log 产生，使用 input

lua/select_character.lua

@@ -1,78 +1,43 @@
 -- 以词定字
--- 来源 https://github.com/BlindingDark/rime-lua-select-character
+-- 原脚本 https://github.com/BlindingDark/rime-lua-select-character
 -- 删除了默认按键 [ ]，和方括号翻页冲突，需要在 key_binder 下指定才能生效
 -- 20230526195910 不再错误地获取commit_text，而是直接获取get_selected_candidate().text。
-local function utf8_sub(s, i, j)
-    i = i or 1
-    j = j or -1
+-- 20240128141207 重写：将读取设置移动到 init 方法中；简化中文取字方法；预先判断候选存在与否，无候选取 input；
 
-    if i < 1 or j < 1 then
-        local n = utf8.len(s)
-        if not n then
-            return nil
-        end
-        if i < 0 then
-            i = n + 1 + i
-        end
-        if j < 0 then
-            j = n + 1 + j
-        end
-        if i < 0 then
-            i = 1
-        elseif i > n then
-            i = n
-        end
-        if j < 0 then
-            j = 1
-        elseif j > n then
-            j = n
-        end
-    end
+local select = {}
 
-    if j < i then
-        return ""
-    end
-
-    i = utf8.offset(s, i)
-    j = utf8.offset(s, j + 1)
-
-    if i and j then
-        return s:sub(i, j - 1)
-    elseif i then
-        return s:sub(i)
-    else
-        return ""
-    end
+function select.init(env)
+    local config = env.engine.schema.config
+    select.first_key = config:get_string('key_binder/select_first_character')
+    select.last_key = config:get_string('key_binder/select_last_character')
 end
 
-local function select_character(key, env)
+function select.func(key, env)
     local engine = env.engine
-    local context = engine.context
-    local commit_text = context:get_commit_text()
-    local config = engine.schema.config
+    local context = env.engine.context
 
-    -- local first_key = config:get_string('key_binder/select_first_character') or 'bracketleft'
-    -- local last_key = config:get_string('key_binder/select_last_character') or 'bracketright'
-    local first_key = config:get_string('key_binder/select_first_character')
-    local last_key = config:get_string('key_binder/select_last_character')
-
-    if context:has_menu() then
-        if (key:repr() == first_key) then
-            if (context:get_selected_candidate().text) then
-                engine:commit_text(utf8_sub(context:get_selected_candidate().text, 1, 1))
+    if
+        not key:release()
+        and (context:is_composing() or context:has_menu())
+        and (select.first_key or select.last_key)
+    then
+        local text = context.input
+        if context:get_selected_candidate() then
+            text = context:get_selected_candidate().text
+        end
+        if utf8.len(text) > 1 then
+            if (key:repr() == select.first_key) then
+                engine:commit_text(text:sub(1, utf8.offset(text, 2) - 1))
                 context:clear()
-            end
-            return 1 -- kAccepted
-        elseif (key:repr() == last_key) then
-            if (context:get_selected_candidate().text) then
-                engine:commit_text(utf8_sub(context:get_selected_candidate().text, -1, -1))
+                return 1
+            elseif (key:repr() == select.last_key) then
+                engine:commit_text(text:sub(utf8.offset(text, -1)))
                 context:clear()
+                return 1
             end
-            return 1 -- kAccepted
         end
     end
-
-    return 2 -- kNoop
+    return 2
 end
 
-return select_character
+return select