-- cursor-warp.lua — Emacs cursor tracking for macOS Zoom
--
-- WHAT: Reads cursor coordinates written by Emacs to ~/.emacs-cursor-pos
--        and posts a real mouseMoved HID event so macOS Zoom follows the
--        text cursor. CGWarpMouseCursorPosition (used by Emacs internally)
--        is silently ignored by macOS Zoom — this workaround fixes that.
--
-- SETUP:
--   1. Install Hammerspoon: https://www.hammerspoon.org/
--   2. Grant Accessibility permission: System Settings → Privacy & Security
--      → Accessibility → enable Hammerspoon
--   3. Copy this file to ~/.hammerspoon/cursor-warp.lua
--   4. In ~/.hammerspoon/init.lua add:  require("cursor-warp")
--   5. In Emacs: SPC z t enables cursor tracking (writes ~/.emacs-cursor-pos)
--   6. Toggle in Hammerspoon: call emacsZoomToggle() or bind a hotkey
--
-- FILE FORMAT (~/.emacs-cursor-pos):
--   Line 1: X Y    (screen-absolute cursor position)
--   Line 2: FX FY  (frame-position, for debug cross-check)

local M = {}

-- Global toggle
emacsZoomEnabled = true
emacsZoomDebug = false

local cursorPosFile = os.getenv("HOME") .. "/.emacs-cursor-pos"
local lastMtime = 0
local pollTimer = nil

local function readCursorPos()
    local f = io.open(cursorPosFile, "r")
    if not f then return nil end
    local line1 = f:read("*l")
    local line2 = f:read("*l")
    f:close()
    if not line1 then return nil end
    local x, y = line1:match("^(%d+) (%d+)$")
    if not x then return nil end
    local fx, fy = nil, nil
    if line2 then
        fx, fy = line2:match("^(%-?%d+) (%-?%d+)$")
    end
    return tonumber(x), tonumber(y), tonumber(fx), tonumber(fy)
end

local function pollAndWarp()
    if not emacsZoomEnabled then return end

    -- Check file modification time to avoid unnecessary reads
    local attrs = hs.fs.attributes(cursorPosFile)
    if not attrs then return end
    local mtime = attrs.modification
    if mtime == lastMtime then return end
    lastMtime = mtime

    local x, y, fx, fy = readCursorPos()
    if not x then return end

    -- Post a real mouseMoved event (not CGWarp)
    hs.eventtap.event.newMouseEvent(
        hs.eventtap.event.types.mouseMoved,
        hs.geometry.point(x, y)
    ):post()

    if emacsZoomDebug then
        local msg = string.format("cursor-warp: move to (%d, %d)", x, y)
        if fx then
            -- Cross-check with Hammerspoon's view of Emacs frame
            local emacs = hs.application.get("Emacs")
            if emacs then
                local win = emacs:focusedWindow()
                if win then
                    local frame = win:frame()
                    msg = msg .. string.format(
                        " | emacs-frame=(%d,%d) hs-frame=(%d,%d)",
                        fx, fy, math.floor(frame.x), math.floor(frame.y))
                end
            end
        end
        print(msg)
    end
end

function emacsZoomToggle()
    emacsZoomEnabled = not emacsZoomEnabled
    local state = emacsZoomEnabled and "ON" or "OFF"
    hs.alert.show("Emacs Zoom tracking: " .. state)
    print("cursor-warp: " .. state)
end

function emacsZoomDebugToggle()
    emacsZoomDebug = not emacsZoomDebug
    hs.alert.show("Emacs Zoom debug: " .. (emacsZoomDebug and "ON" or "OFF"))
end

-- Start polling
pollTimer = hs.timer.doEvery(0.05, pollAndWarp)

-- Optional hotkey: Ctrl+Opt+Cmd+Z to toggle
hs.hotkey.bind({"ctrl", "alt", "cmd"}, "Z", emacsZoomToggle)

print("cursor-warp: loaded (polling every 50ms, hotkey Ctrl+Opt+Cmd+Z)")

return M