From de719553fddc381e274d8bff218ab4e3f6691945 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Fri, 31 May 2024 17:15:06 -0400
Subject: Add timers.lua API module and test_timers.lua test program.

Since timers presents a timers.Timer Lua class supporting queries and
cancellation, make TimersListener::scheduleAfter() and scheduleEvery() respond
immediately so the newly constructed Timer object has the reqid necessary to
perform those subsequent operations.

This requires that Lua invocations of these operations avoid calling the
caller's callback with that initial response.

Reinvent leap.generate() to return a Lua object supporting next() and done()
methods. A plain Lua coroutine that (indirectly) calls fiber.wait() confuses
the fiber scheduler, so avoid implementing generate() as a Lua coroutine.

Add a bit more leap.lua diagnostic output.
---
 indra/newview/scripts/lua/timers.lua | 101 +++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 indra/newview/scripts/lua/timers.lua

(limited to 'indra/newview/scripts/lua/timers.lua')

diff --git a/indra/newview/scripts/lua/timers.lua b/indra/newview/scripts/lua/timers.lua
new file mode 100644
index 0000000000..e0d27a680d
--- /dev/null
+++ b/indra/newview/scripts/lua/timers.lua
@@ -0,0 +1,101 @@
+-- Access to the viewer's time-delay facilities
+
+local leap = require 'leap'
+
+local timers = {}
+
+local function dbg(...) end
+-- local dbg = require 'printf'
+
+timers.Timer = {}
+
+-- delay:    time in seconds until callback
+-- callback: 'wait', or function to call when timer fires (self:tick if nil)
+-- iterate:  if non-nil, call callback repeatedly until it returns non-nil
+--           (ignored if 'wait')
+function timers.Timer:new(delay, callback, iterate)
+    local obj = setmetatable({}, self)
+    self.__index = self
+
+    if callback == 'wait' then
+        dbg('scheduleAfter(%d):', delay)
+        sequence = leap.generate('Timers', {op='scheduleAfter', after=delay})
+        -- ignore the immediate return
+        dbg('scheduleAfter(%d) -> %s', delay,
+        sequence.next())
+        -- this call is where we wait for real
+        dbg('next():')
+        dbg('next() -> %s',
+        sequence.next())
+        sequence.done()
+        return
+    end
+
+    callback = callback or function() obj:tick() end
+
+    local first = true
+    if iterate then
+        obj.id = leap.eventstream(
+            'Timers',
+            {op='scheduleEvery', every=delay},
+            function (event)
+                local reqid = event.reqid
+                if first then
+                    first = false
+                    dbg('timer(%s) first callback', reqid)
+                    -- discard the first (immediate) response: don't call callback
+                    return nil
+                else
+                    dbg('timer(%s) nth callback', reqid)
+                    return callback(event)
+                end
+            end
+        ).reqid
+    else
+        obj.id = leap.eventstream(
+            'Timers',
+            {op='scheduleAfter', after=delay},
+            function (event)
+                -- Arrange to return nil the first time, true the second. This
+                -- callback is called immediately with the response to
+                -- 'scheduleAfter', and if we immediately returned true, we'd
+                -- be done, and the subsequent timer event would be discarded.
+                if first then
+                    first = false
+                    -- Caller doesn't expect an immediate callback.
+                    return nil
+                else
+                    callback(event)
+                    -- Since caller doesn't want to iterate, the value
+                    -- returned by the callback is irrelevant: just stop after
+                    -- this one and only call.
+                    return true
+                end
+            end
+        ).reqid
+    end
+
+    return obj
+end
+
+function timers.Timer:tick()
+    error('Pass a callback to Timer:new(), or override Timer:tick()')
+end
+
+function timers.Timer:cancel()
+    local ok = leap.request('Timers', {op='cancel', id=self.id}).ok
+    leap.cancelreq(self.id)
+    return ok
+end
+
+function timers.Timer:isRunning()
+    return leap.request('Timers', {op='isRunning', id=self.id}).running
+end
+
+-- returns (true, seconds left) for a live timer, else (false, 0)
+function timers.Timer:timeUntilCall()
+    local result = leap.request('Timers', {op='timeUntilCall', id=self.id})
+    return result.ok, result.remaining
+end
+
+return timers
-- 
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