add async managers (#536)

1 files changed, 90 insertions, 0 deletions

diff --git a/lua/nvim-lsp-installer/core/optional.lua b/lua/nvim-lsp-installer/core/optional.lua
new file mode 100644
index 00000000..d37a7e69
--- /dev/null
+++ b/lua/nvim-lsp-installer/core/optional.lua
@@ -0,0 +1,90 @@
+---@class Optional
+---@field private _value unknown
+local Optional = {}
+Optional.__index = Optional
+
+---@param value any
+function Optional.new(value)
+    return setmetatable({ _value = value }, Optional)
+end
+
+local EMPTY = Optional.new(nil)
+
+---@param value any
+function Optional.of_nilable(value)
+    if value == nil then
+        return EMPTY
+    else
+        return Optional.new(value)
+    end
+end
+
+function Optional.empty()
+    return EMPTY
+end
+
+---@param value any
+function Optional.of(value)
+    return Optional.new(value)
+end
+
+---@param mapper_fn fun(value: any): any
+function Optional:map(mapper_fn)
+    if self:is_present() then
+        return Optional.of_nilable(mapper_fn(self._value))
+    else
+        return EMPTY
+    end
+end
+
+function Optional:get()
+    if not self:is_present() then
+        error("No value present.", 2)
+    end
+    return self._value
+end
+
+---@param value any
+function Optional:or_else(value)
+    if self:is_present() then
+        return self._value
+    else
+        return value
+    end
+end
+
+---@param supplier fun(): Optional
+function Optional:when_empty(supplier)
+    if self:is_present() then
+        return self._value
+    else
+        return supplier()
+    end
+end
+
+---@param exception any @(optional) The exception to throw if the result is a failure.
+function Optional:or_else_throw(exception)
+    if self:is_present() then
+        return self._value
+    else
+        if exception then
+            error(exception, 2)
+        else
+            error("No value present.", 2)
+        end
+    end
+end
+
+---@param fn fun(value: any)
+function Optional:if_present(fn)
+    if self:is_present() then
+        fn(self._value)
+    end
+    return self
+end
+
+function Optional:is_present()
+    return self._value ~= nil
+end
+
+return Optional