Plays a NesHawk movie on SubNesHawk

neshawk2subneshawk.lua

--[[
Plays a NesHawk movie on SubNesHawk.

Set INPUT_PATH, and launch this script (at frame 0).

Power/Reset is not supported.
--]]

-- extract "Input Log.txt" from your NesHawk movie, and put it to the script directory.
-- (or specify an absolute path)
local INPUT_PATH  = "Input Log.txt"

local function str_at(s, idx)
    return string.sub(s, idx, idx)
end

local function str_starts_with(s, prefix)
    return string.find(s, prefix, 1, true) == 1
end

local function panic(msg)
    error(msg)
end

-- parses a player input. (e.g. "UDLRSsBA")
local function parse_input_player(s)
    local CHARS = { "U", "D", "L", "R", "S", "s", "B", "A" }
    local NAMES = { "Up", "Down", "Left", "Right", "Start", "Select", "B", "A" }

    if string.len(s) ~= 8 then
        return nil
    end

    local input = {}

    for i = 1, 8 do
        local ch = str_at(s, i)
        if ch == "." then
            -- do nothing
        elseif ch == CHARS[i] then
            input[NAMES[i]] = true
        else
            return nil
        end
    end

    return input
end

-- parses a frame line. (e.g. "|..|UDLRSsBA|")
local function parse_input_frame(line)
    local invalid = function ()
        panic(string.format("invalid input frame: %s", line))
    end

    if not str_starts_with(line, "|") then
        invalid()
    end

    -- current position in the line.
    local pos = 2

    -- skip power/reset field.
    do
        local pos_sep = string.find(line, "|", pos, true)
        if pos_sep == nil then
            invalid()
        end
        pos = pos_sep + 1
    end

    -- array for each player's input.
    local inputs = {}

    -- parse inputs, up to 4 players.
    for _i = 1, 4 do
        local pos_sep = string.find(line, "|", pos, true)
        if pos_sep == nil then
            break
        end

        local s = string.sub(line, pos, pos_sep - 1)
        local input = parse_input_player(s)
        if input == nil then
            invalid()
        end
        table.insert(inputs, input)

        pos = pos_sep + 1
    end

    -- at least, player 1's input must exist.
    if #inputs == 0 then
        invalid()
    end

    return inputs
end

-- parses "Input Log.txt".
local function parse_input(path)
    local rdr = io.open(path, "r")
    if rdr == nil then
        panic(string.format("can't open file '%s'", path))
    end

    local lines = rdr:lines()

    -- check for header.
    do
        local line_first = lines()
        if line_first ~= "[Input]" then
            panic("invalid input: '[Input]' not found")
        end

        local line_second = lines()
        if not str_starts_with(line_second, "LogKey:") then
            panic("invalid input: 'LogKey:' not found")
        end
    end

    -- array for each frame.
    local frames = {}

    -- parse each frames.
    for line in rdr:lines() do
        if line == "[/Input]" then
            break
        end

        local inputs = parse_input_frame(line)
        table.insert(frames, inputs)
    end

    rdr:close()

    return frames
end

local function play(frames)
    -- NOTE: you can't use emu.islagged() to detect VSYNC.
    -- use emu.lagcount().

    local frame = emu.lagcount()

    for _i, inputs in ipairs(frames) do
        repeat
            for j, input in ipairs(inputs) do
                joypad.set(input, j)
            end
            emu.frameadvance()
        until frame ~= emu.lagcount()

        frame = emu.lagcount()
    end
end

local function main()
    local frames = parse_input(INPUT_PATH)

    play(frames)
end

main()