-- probe.lua -- frame snapshots + marker/PC telemetry for the GUI experiments.
--
--   MSG_TRIGGER=<path>  "<prefix> <count> <stride>" -> PNG snapshots
--   MSG_DIR=<dir>       where PNGs go
--
-- Also prints a marker line every 250 frames, so a wedged machine still leaves
-- evidence of how far the injected payload got:
--   01850100 display   01850110 root   01850120 window
--   01850130 sync      01850140 stage  01850150 strlen
local machine = manager.machine
local dir = os.getenv("MSG_DIR") or "."
local trigger = os.getenv("MSG_TRIGGER") or (dir .. "/trigger")
local screen = nil
for _, s in pairs(machine.screens) do screen = s; break end
local cpu = machine.devices[':maincpu']
local space = cpu.spaces['program']

local frame = 0
local job = nil

local function consume_trigger()
    local fh = io.open(trigger, "r")
    if not fh then return end
    local text = fh:read("*a") or ""
    fh:close()
    os.remove(trigger)
    local prefix, count, stride = text:match("(%S+)%s+(%d+)%s+(%d+)")
    if not prefix then
        print("probe: bad trigger " .. text)
        return
    end
    job = { prefix = prefix, left = tonumber(count), stride = tonumber(stride), next = frame }
    print(string.format("probe: frame %d job %s x%d every %d", frame,
                        prefix, job.left, job.stride))
end

local function u32(addr)
    local ok, v = pcall(function() return space:read_u32(addr) end)
    if ok then return v end
    return 0xdeadbeef
end

emu.register_frame_done(function()
    frame = frame + 1
    consume_trigger()
    if job and frame >= job.next and screen then
        local out = string.format("%s/%s_frame%05d.png", dir, job.prefix, frame)
        local ok, err = pcall(function() return screen:snapshot(out) end)
        print(string.format("probe: frame %d %s ok=%s err=%s", frame,
                            out, tostring(ok), tostring(err)))
        job.left = job.left - 1
        job.next = frame + job.stride
        if job.left <= 0 then job = nil end
    end
    if frame % 250 == 0 then
        print(string.format("probe: frame %d PC=%08X disp=%08X root=%08X win=%08X sync=%08X stage=%d strlen=%d",
            frame, cpu.state['PC'].value,
            u32(0x01850100), u32(0x01850110), u32(0x01850120),
            u32(0x01850130), u32(0x01850140), u32(0x01850150)))
    end
end, "vt1200-gui-probe")

if machine.debugger then machine.debugger.execution_state = 'run' end