Add small user interaction module

For now, only contains a `yes_no_prompt` function.

cyan-dev-1.rockspec

@@ -32,6 +32,7 @@ build = {
       ["cyan.fs.init"] = "build/cyan/fs/init.lua",
       ["cyan.fs.path"] = "build/cyan/fs/path.lua",
       ["cyan.graph"] = "build/cyan/graph.lua",
+      ["cyan.interaction"] = "build/cyan/interaction.lua",
       ["cyan.log"] = "build/cyan/log.lua",
       ["cyan.meta"] = "build/cyan/meta.lua",
       ["cyan.sandbox"] = "build/cyan/sandbox.lua",
@@ -54,6 +55,7 @@ build = {
          ["cyan.fs.init"] = "src/cyan/fs/init.tl",
          ["cyan.fs.path"] = "src/cyan/fs/path.tl",
          ["cyan.graph"] = "src/cyan/graph.tl",
+         ["cyan.interaction"] = "src/cyan/interaction.tl",
          ["cyan.log"] = "src/cyan/log.tl",
          ["cyan.meta"] = "src/cyan/meta.tl",
          ["cyan.sandbox"] = "src/cyan/sandbox.tl",

src/cyan/interaction.tl

@@ -0,0 +1,82 @@
+---@brief
+--- Module for handling when input from the user is needed
+
+local log <const> = require("cyan.log")
+local cs <const> = require("cyan.colorstring")
+local ansi <const> = require("cyan.ansi")
+
+local interaction <const> = {}
+
+local affirmative <const> = { ansi.color.dark.green }
+local negative <const> = { ansi.color.dark.red }
+
+local yesses <const> = { "yes", "yeah", "yea", "ye", "y" }
+local nos <const> = { "no", "nope", "n" }
+
+local function title_case(s: string): string
+   return s:sub(1, 1):upper() .. s:sub(2, -1):lower()
+end
+
+local function to_string_set(list: {string}): {string:boolean}
+   local result <const> = {}
+   for _, v in ipairs(list) do
+      result[v:lower()] = true
+   end
+   return result
+end
+
+---@desc
+--- Ask the user to affirm or deny a given prompt. The user input will be
+--- compared against the given `affirm` and `deny` lists (case-insensitive), with
+--- defaults used if - they are not provided.
+---
+--- The given logger will be used to print the prompt, and `log.info` if none
+--- is provided.
+function interaction.yes_no_prompt(
+   prompt: string,
+   logger: log.Logger,
+   default: boolean,
+   affirm: {string},
+   deny: {string}
+): boolean
+   logger = logger or log.info
+   affirm = affirm or yesses
+   deny = deny or nos
+
+   local y <const> = cs.highlight(
+      affirmative,
+      default and title_case(affirm[1]) or affirm[1]:lower()
+   )
+   local n <const> = cs.highlight(
+      negative,
+      default and deny[1]:lower() or title_case(deny[1])
+   )
+   local prompt_str <const> = prompt .. " [" .. y .. "/" .. n .. "]: "
+
+   local affirm_set <const> = to_string_set(affirm)
+   local deny_set <const> = to_string_set(deny)
+
+   while true do
+      logger:nonl(prompt_str)
+      logger.stream:flush()
+      local input = io.read("*l"):lower()
+
+      if #input == 0 then
+         logger:cont(
+            "Defaulting to ",
+            default
+               and cs.highlight(affirmative, title_case(affirm[1]))
+               or cs.highlight(negative, title_case(deny[1]))
+         )
+         return default or false
+      end
+
+      if affirm_set[input] then
+         return true
+      elseif deny_set[input] then
+         return false
+      end
+   end
+end
+
+return interaction