[V3 Context] Interactive sending of multiple messages (#1081)

* Interactive pages method for context

* Use new methods in dev

* Undo code formatting

* Rename method to be more generalised

* More general arg

redbot/core/context.py

@@ -1,12 +1,15 @@
-"""Module for Red's Context class
-
+"""
 The purpose of this module is to allow for Red to further customise the command
 invocation context provided by discord.py.
 """
+import asyncio
+from typing import Iterable, List
 
 import discord
 from discord.ext import commands
 
+from redbot.core.utils.chat_formatting import box
+
 __all__ = ["RedContext"]
 
 TICK = "\N{WHITE HEAVY CHECK MARK}"
@@ -20,9 +23,9 @@ class RedContext(commands.Context):
     This class inherits from `commands.Context <discord.ext.commands.Context>`.
     """
 
-    async def send_help(self):
+    async def send_help(self) -> List[discord.Message]:
         """Send the command help message.
-        
+
         Returns
         -------
         `list` of `discord.Message`
@@ -36,7 +39,7 @@ class RedContext(commands.Context):
             ret.append(await self.send(page))
         return ret
 
-    async def tick(self):
+    async def tick(self) -> bool:
         """Add a tick reaction to the command message.
 
         Returns
@@ -51,3 +54,60 @@ class RedContext(commands.Context):
             return False
         else:
             return True
+
+    async def send_interactive(self,
+                               messages: Iterable[str],
+                               box_lang: str=None,
+                               timeout: int=15) -> List[discord.Message]:
+        """Send multiple messages interactively.
+
+        The user will be prompted for whether or not they would like to view
+        the next message, one at a time. They will also be notified of how
+        many messages are remaining on each prompt.
+
+        Parameters
+        ----------
+        messages : `iterable` of `str`
+            The messages to send.
+        box_lang : str
+            If specified, each message will be contained within a codeblock of
+            this language.
+        timeout : int
+            How long the user has to respond to the prompt before it times out.
+            After timing out, the bot deletes its prompt message.
+
+        """
+        messages = tuple(messages)
+        ret = []
+
+        more_check = lambda m: (m.author == self.author and
+                                m.channel == self.channel and
+                                m.content.lower() == "more")
+
+        for idx, page in enumerate(messages, 1):
+            if box_lang is None:
+                msg = await self.send(page)
+            else:
+                msg = await self.send(box(page, lang=box_lang))
+            ret.append(msg)
+            n_remaining = len(messages) - idx
+            if n_remaining > 0:
+                if n_remaining == 1:
+                    plural = ""
+                    is_are = "is"
+                else:
+                    plural = "s"
+                    is_are = "are"
+                query = await self.send(
+                    "There {} still {} message{} remaining. "
+                    "Type `more` to continue."
+                    "".format(is_are, n_remaining, plural))
+                try:
+                    resp = await self.bot.wait_for(
+                        'message', check=more_check, timeout=timeout)
+                except asyncio.TimeoutError:
+                    await query.delete()
+                    break
+                else:
+                    await self.channel.delete_messages((query, resp))
+        return ret