-- Display some stats.
--
-- Please consult the readme for information about usage and configuration:
-- https://github.com/Argon-/mpv-stats
--
-- Please note: not every property is always available and therefore not always
-- visible.

local mp = require 'mp'
local options = require 'mp.options'
local utils = require 'mp.utils'

-- Options
local o = {
    -- Default key bindings
    key_oneshot = "i",
    key_toggle = "I",
    key_page_1 = "1",
    key_page_2 = "2",
    key_page_3 = "3",

    duration = 4,
    redraw_delay = 1,                -- acts as duration in the toggling case
    ass_formatting = true,
    persistent_overlay = false,      -- whether the stats can be overwritten by other output
    print_perfdata_passes = false,   -- when true, print the full information about all passes
    filter_params_max_length = 100,  -- a filter list longer than this many characters will be shown one filter per line instead
    debug = false,

    -- Graph options and style
    plot_perfdata = true,
    plot_vsync_ratio = true,
    plot_vsync_jitter = true,
    skip_frames = 5,
    global_max = true,
    flush_graph_data = true,         -- clear data buffers when toggling
    plot_bg_border_color = "0000FF",
    plot_bg_color = "262626",
    plot_color = "FFFFFF",

    -- Text style
    font = "sans",
    font_mono = "monospace",   -- monospaced digits are sufficient
    font_size = 8,
    font_color = "FFFFFF",
    border_size = 0.8,
    border_color = "262626",
    shadow_x_offset = 0.0,
    shadow_y_offset = 0.0,
    shadow_color = "000000",
    alpha = "11",

    -- Custom header for ASS tags to style the text output.
    -- Specifying this will ignore the text style values above and just
    -- use this string instead.
    custom_header = "",

    -- Text formatting
    -- With ASS
    ass_nl = "\\N",
    ass_indent = "\\h\\h\\h\\h\\h",
    ass_prefix_sep = "\\h\\h",
    ass_b1 = "{\\b1}",
    ass_b0 = "{\\b0}",
    ass_it1 = "{\\i1}",
    ass_it0 = "{\\i0}",
    -- Without ASS
    no_ass_nl = "\n",
    no_ass_indent = "\t",
    no_ass_prefix_sep = " ",
    no_ass_b1 = "\027[1m",
    no_ass_b0 = "\027[0m",
    no_ass_it1 = "\027[3m",
    no_ass_it0 = "\027[0m",
}
options.read_options(o)

local format = string.format
local max = math.max
local min = math.min

-- Function used to record performance data
local recorder = nil
-- Timer used for redrawing (toggling) and clearing the screen (oneshot)
local display_timer = nil
-- Timer used to update cache stats.
local cache_recorder_timer = nil
-- Current page and <page key>:<page function> mappings
local curr_page = o.key_page_1
local pages = {}
-- Save these sequences locally as we'll need them a lot
local ass_start = mp.get_property_osd("osd-ass-cc/0")
local ass_stop = mp.get_property_osd("osd-ass-cc/1")
-- Ring buffers for the values used to construct a graph.
-- .pos denotes the current position, .len the buffer length
-- .max is the max value in the corresponding buffer
local vsratio_buf, vsjitter_buf, cache_ahead_buf, cache_total_buf
local function init_buffers()
    vsratio_buf = {0, pos = 1, len = 50, max = 0}
    vsjitter_buf = {0, pos = 1, len = 50, max = 0}
    cache_ahead_buf = {0, pos = 1, len = 50, max = 0}
    cache_total_buf = {0, pos = 1, len = 50, max = 0}
end
-- Save all properties known to this version of mpv
local property_list = {}
for p in string.gmatch(mp.get_property("property-list"), "([^,]+)") do property_list[p] = true end
-- Mapping of properties to their deprecated names
local property_aliases = {
    ["decoder-frame-drop-count"] = "drop-frame-count",
    ["frame-drop-count"] = "vo-drop-frame-count",
    ["container-fps"] = "fps",
}


-- Return deprecated name for the given property
local function compat(p)
    while not property_list[p] and property_aliases[p] do
        p = property_aliases[p]
    end
    return p
end


local function set_ASS(b)
    if not o.use_ass or o.persistent_overlay then
        return ""
    end
    return b and ass_start or ass_stop
end


local function no_ASS(t)
    return set_ASS(false) .. t .. set_ASS(true)
end


local function b(t)
    return o.b1 .. t .. o.b0
end


local function it(t)
    return o.it1 .. t .. o.it0
end


local function text_style()
    if not o.use_ass then
        return ""
    end
    if o.custom_header and o.custom_header ~= "" then
        return set_ASS(true) .. o.custom_header
    else
        return format("%s{\\r}{\\an7}{\\fs%d}{\\fn%s}{\\bord%f}{\\3c&H%s&}" ..
                      "{\\1c&H%s&}{\\alpha&H%s&}{\\xshad%f}{\\yshad%f}{\\4c&H%s&}",
                      set_ASS(true), o.font_size, o.font, o.border_size,
                      o.border_color, o.font_color, o.alpha, o.shadow_x_offset,
                      o.shadow_y_offset, o.shadow_color)
    end
end


local function has_vo_window()
    return mp.get_property("vo-configured") == "yes"
end


local function has_ansi()
    local is_windows = type(package) == 'table'
        and type(package.config) == 'string'
        and package.config:sub(1, 1) == '\\'
    if is_windows then
        return os.getenv("ANSICON")
    end
    return true
end


-- Generate a graph from the given values.
-- Returns an ASS formatted vector drawing as string.
--
-- values: Array/table of numbers representing the data. Used like a ring buffer
--         it will get iterated backwards `len` times starting at position `i`.
-- i     : Index of the latest data value in `values`.
-- len   : The length/amount of numbers in `values`.
-- v_max : The maximum number in `values`. It is used to scale all data
--         values to a range of 0 to `v_max`.
-- v_avg : The average number in `values`. It is used to try and center graphs
--         if possible. May be left as nil
-- scale : A value that will be multiplied with all data values.
-- x_tics: Horizontal width multiplier for the steps
local function generate_graph(values, i, len, v_max, v_avg, scale, x_tics)
    -- Check if at least one value exists
    if not values[i] then
        return ""
    end

    local x_max = (len - 1) * x_tics
    local y_offset = o.border_size
    local y_max = o.font_size * 0.66
    local x = 0

    -- try and center the graph if possible, but avoid going above `scale`
    if v_avg then
        scale = min(scale, v_max / (2 * v_avg))
    end

    local s = {format("m 0 0 n %f %f l ", x, y_max - (y_max * values[i] / v_max * scale))}
    i = ((i - 2) % len) + 1

    for p = 1, len - 1 do
        if values[i] then
            x = x - x_tics
            s[#s+1] = format("%f %f ", x, y_max - (y_max * values[i] / v_max * scale))
        end
        i = ((i - 2) % len) + 1
    end

    s[#s+1] = format("%f %f %f %f", x, y_max, 0, y_max)

    local bg_box = format("{\\bord0.5}{\\3c&H%s&}{\\1c&H%s&}m 0 %f l %f %f %f 0 0 0",
                          o.plot_bg_border_color, o.plot_bg_color, y_max, x_max, y_max, x_max)
    return format("%s{\\r}{\\pbo%f}{\\shad0}{\\alpha&H00}{\\p1}%s{\\p0}{\\bord0}{\\1c&H%s}{\\p1}%s{\\p0}%s",
                  o.prefix_sep, y_offset, bg_box, o.plot_color, table.concat(s), text_style())
end


local function append(s, str, attr)
    if not str then
        return false
    end
    attr.prefix_sep = attr.prefix_sep or o.prefix_sep
    attr.indent = attr.indent or o.indent
    attr.nl = attr.nl or o.nl
    attr.suffix = attr.suffix or ""
    attr.prefix = attr.prefix or ""
    attr.no_prefix_markup = attr.no_prefix_markup or false
    attr.prefix = attr.no_prefix_markup and attr.prefix or b(attr.prefix)
    s[#s+1] = format("%s%s%s%s%s%s", attr.nl, attr.indent,
                     attr.prefix, attr.prefix_sep, no_ASS(str), attr.suffix)
    return true
end


-- Format and append a property.
-- A property whose value is either `nil` or empty (hereafter called "invalid")
-- is skipped and not appended.
-- Returns `false` in case nothing was appended, otherwise `true`.
--
-- s      : Table containing strings.
-- prop   : The property to query and format (based on its OSD representation).
-- attr   : Optional table to overwrite certain (formatting) attributes for
--          this property.
-- exclude: Optional table containing keys which are considered invalid values
--          for this property. Specifying this will replace empty string as
--          default invalid value (nil is always invalid).
local function append_property(s, prop, attr, excluded)
    excluded = excluded or {[""] = true}
    local ret = mp.get_property_osd(prop)
    if not ret or excluded[ret] then
        if o.debug then
            print("No value for property: " .. prop)
        end
        return false
    end
    return append(s, ret, attr)
end


local function append_perfdata(s, dedicated_page)
    local vo_p = mp.get_property_native("vo-passes")
    if not vo_p then
        return
    end

    local ds = mp.get_property_bool("display-sync-active", false)
    local target_fps = ds and mp.get_property_number("display-fps", 0)
                       or mp.get_property_number(compat("container-fps"), 0)
    if target_fps > 0 then target_fps = 1 / target_fps * 1e9 end

    -- Sums of all last/avg/peak values
    local last_s, avg_s, peak_s = {}, {}, {}
    for frame, data in pairs(vo_p) do
        last_s[frame], avg_s[frame], peak_s[frame] = 0, 0, 0
        for _, pass in ipairs(data) do
            last_s[frame] = last_s[frame] + pass["last"]
            avg_s[frame]  = avg_s[frame]  + pass["avg"]
            peak_s[frame] = peak_s[frame] + pass["peak"]
        end
    end

    -- Pretty print measured time
    local function pp(i)
        -- rescale to microseconds for a saner display
        return format("%05d", i / 1000)
    end

    -- Format n/m with a font weight based on the ratio
    local function p(n, m)
        local i = 0
        if m > 0 then
            i = tonumber(n) / m
        end
        -- Calculate font weight. 100 is minimum, 400 is normal, 700 bold, 900 is max
        local w = (700 * math.sqrt(i)) + 200
        return format("{\\b%d}%02d%%{\\b0}", w, i * 100)
    end

    s[#s+1] = format("%s%s%s%s{\\fs%s}%s{\\fs%s}",
                     dedicated_page and "" or o.nl, dedicated_page and "" or o.indent,
                     b("Frame Timings:"), o.prefix_sep, o.font_size * 0.66,
                     "(last/average/peak  μs)", o.font_size)

    for frame, data in pairs(vo_p) do
        local f = "%s%s%s{\\fn%s}%s / %s / %s %s%s{\\fn%s}%s%s%s"

        if dedicated_page then
            s[#s+1] = format("%s%s%s:", o.nl, o.indent,
                             b(frame:gsub("^%l", string.upper)))

            for _, pass in ipairs(data) do
                s[#s+1] = format(f, o.nl, o.indent, o.indent,
                                 o.font_mono, pp(pass["last"]),
                                 pp(pass["avg"]), pp(pass["peak"]),
                                 o.prefix_sep .. o.prefix_sep, p(pass["last"], last_s[frame]),
                                 o.font, o.prefix_sep, o.prefix_sep, pass["desc"])

                if o.plot_perfdata and o.use_ass then
                    s[#s+1] = generate_graph(pass["samples"], pass["count"],
                                             pass["count"], pass["peak"],
                                             pass["avg"], 0.9, 0.25)
                end
            end

            -- Print sum of timing values as "Total"
            s[#s+1] = format(f, o.nl, o.indent, o.indent,
                             o.font_mono, pp(last_s[frame]),
                             pp(avg_s[frame]), pp(peak_s[frame]), "", "", o.font,
                             o.prefix_sep, o.prefix_sep, b("Total"))
        else
            -- for the simplified view, we just print the sum of each pass
            s[#s+1] = format(f, o.nl, o.indent, o.indent, o.font_mono,
                            pp(last_s[frame]), pp(avg_s[frame]), pp(peak_s[frame]),
                            "", "", o.font, o.prefix_sep, o.prefix_sep,
                            frame:gsub("^%l", string.upper))
        end
    end
end


local function append_display_sync(s)
    if not mp.get_property_bool("display-sync-active", false) then
        return
    end

    local vspeed = append_property(s, "video-speed-correction", {prefix="DS:"})
    if vspeed then
        append_property(s, "audio-speed-correction",
                        {prefix="/", nl="", indent=" ", prefix_sep=" ", no_prefix_markup=true})
    else
        append_property(s, "audio-speed-correction",
                        {prefix="DS:" .. o.prefix_sep .. " - / ", prefix_sep=""})
    end

    append_property(s, "mistimed-frame-count", {prefix="Mistimed:", nl=""})
    append_property(s, "vo-delayed-frame-count", {prefix="Delayed:", nl=""})

    -- As we need to plot some graphs we print jitter and ratio on their own lines
    if not display_timer.oneshot and (o.plot_vsync_ratio or o.plot_vsync_jitter) and o.use_ass then
        local ratio_graph = ""
        local jitter_graph = ""
        if o.plot_vsync_ratio then
            ratio_graph = generate_graph(vsratio_buf, vsratio_buf.pos, vsratio_buf.len, vsratio_buf.max, nil, 0.8, 1)
        end
        if o.plot_vsync_jitter then
            jitter_graph = generate_graph(vsjitter_buf, vsjitter_buf.pos, vsjitter_buf.len, vsjitter_buf.max, nil, 0.8, 1)
        end
        append_property(s, "vsync-ratio", {prefix="VSync Ratio:", suffix=o.prefix_sep .. ratio_graph})
        append_property(s, "vsync-jitter", {prefix="VSync Jitter:", suffix=o.prefix_sep .. jitter_graph})
    else
        -- Since no graph is needed we can print ratio/jitter on the same line and save some space
        local vratio = append_property(s, "vsync-ratio", {prefix="VSync Ratio:"})
        append_property(s, "vsync-jitter", {prefix="VSync Jitter:", nl="" or o.nl})
    end
end


local function append_filters(s, prop, prefix)
    local length = 0
    local filters = {}

    for _,f in ipairs(mp.get_property_native(prop, {})) do
        local n = f.name
        if f.enabled ~= nil and not f.enabled then
            n = n .. " (disabled)"
        end

        local p = {}
        for key,value in pairs(f.params) do
            p[#p+1] = key .. "=" .. value
        end
        if #p > 0 then
            p = " [" .. table.concat(p, " ") .. "]"
        else
            p = ""
        end

        length = length + n:len() + p:len()
        filters[#filters+1] = no_ASS(n) .. it(no_ASS(p))
    end

    if #filters > 0 then
        local ret
        if length < o.filter_params_max_length then
            ret = table.concat(filters, ", ")
        else
            local sep = o.nl .. o.indent .. o.indent
            ret = sep .. table.concat(filters, sep)
        end
        s[#s+1] = o.nl .. o.indent .. b(prefix) .. o.prefix_sep .. ret
    end
end


local function add_header(s)
    s[#s+1] = text_style()
end


local function add_file(s)
    append(s, "", {prefix="File:", nl="", indent=""})
    append_property(s, "filename", {prefix_sep="", nl="", indent=""})
    if not (mp.get_property_osd("filename") == mp.get_property_osd("media-title")) then
        append_property(s, "media-title", {prefix="Title:"})
    end

    local fs = append_property(s, "file-size", {prefix="Size:"})
    append_property(s, "file-format", {prefix="Format/Protocol:", nl=fs and "" or o.nl})

    local ch_index = mp.get_property_number("chapter")
    if ch_index and ch_index >= 0 then
        append_property(s, "chapter-list/" .. tostring(ch_index) .. "/title", {prefix="Chapter:"})
        append_property(s, "chapter-list/count",
                        {prefix="(" .. tostring(ch_index + 1) .. "/", suffix=")", nl="",
                         indent=" ", prefix_sep=" ", no_prefix_markup=true})
    end

    local demuxer_cache = mp.get_property_native("demuxer-cache-state", {})
    if demuxer_cache["fw-bytes"] then
        demuxer_cache = demuxer_cache["fw-bytes"] -- returns bytes
    else
        demuxer_cache = 0
    end
    local demuxer_secs = mp.get_property_number("demuxer-cache-duration", 0)
    if demuxer_cache + demuxer_secs > 0 then
        append(s, utils.format_bytes_humanized(demuxer_cache), {prefix="Total Cache:"})
        append(s, format("%.1f", demuxer_secs), {prefix="(", suffix=" sec)", nl="",
               no_prefix_markup=true, prefix_sep="", indent=o.prefix_sep})
        local speed = mp.get_property_number("cache-speed", 0)
        if speed > 0 then
            append(s, utils.format_bytes_humanized(speed) .. "/s", {prefix="Speed:", nl="",
                   indent=o.prefix_sep, no_prefix_markup=true})
        end
    end
end


local function add_video(s)
    local r = mp.get_property_native("video-params")
    -- in case of e.g. lavi-complex there can be no input video, only output
    if not r then
        r = mp.get_property_native("video-out-params")
    end
    if not r then
        return
    end

    append(s, "", {prefix=o.nl .. o.nl .. "Video:", nl="", indent=""})
    if append_property(s, "video-codec", {prefix_sep="", nl="", indent=""}) then
        append_property(s, "hwdec-current", {prefix="(hwdec:", nl="", indent=" ",
                         no_prefix_markup=true, suffix=")"}, {no=true, [""]=true})
    end
    append_property(s, "avsync", {prefix="A-V:"})
    if append_property(s, compat("decoder-frame-drop-count"),
                       {prefix="Dropped Frames:", suffix=" (decoder)"}) then
        append_property(s, compat("frame-drop-count"), {suffix=" (output)", nl="", indent=""})
    end
    if append_property(s, "display-fps", {prefix="Display FPS:", suffix=" (specified)"}) then
        append_property(s, "estimated-display-fps",
                        {suffix=" (estimated)", nl="", indent=""})
    else
        append_property(s, "estimated-display-fps",
                        {prefix="Display FPS:", suffix=" (estimated)"})
    end
    if append_property(s, compat("container-fps"), {prefix="FPS:", suffix=" (specified)"}) then
        append_property(s, "estimated-vf-fps",
                        {suffix=" (estimated)", nl="", indent=""})
    else
        append_property(s, "estimated-vf-fps",
                        {prefix="FPS:", suffix=" (estimated)"})
    end

    append_display_sync(s)
    append_perfdata(s, o.print_perfdata_passes)

    if append(s, r["w"], {prefix="Native Resolution:"}) then
        append(s, r["h"], {prefix="x", nl="", indent=" ", prefix_sep=" ", no_prefix_markup=true})
    end
    append_property(s, "current-window-scale", {prefix="Window Scale:"})
    append(s, format("%.2f", r["aspect"]), {prefix="Aspect Ratio:"})
    append(s, r["pixelformat"], {prefix="Pixel Format:"})

    -- Group these together to save vertical space
    local prim = append(s, r["primaries"], {prefix="Primaries:"})
    local cmat = append(s, r["colormatrix"], {prefix="Colormatrix:", nl=prim and "" or o.nl})
    append(s, r["colorlevels"], {prefix="Levels:", nl=cmat and "" or o.nl})

    -- Append HDR metadata conditionally (only when present and interesting)
    local hdrpeak = r["sig-peak"] or 0
    local hdrinfo = ""
    if hdrpeak > 1 then
        hdrinfo = " (HDR peak: " .. format("%.2f", hdrpeak) .. ")"
    end

    append(s, r["gamma"], {prefix="Gamma:", suffix=hdrinfo})
    append_property(s, "packet-video-bitrate", {prefix="Bitrate:", suffix=" kbps"})
    append_filters(s, "vf", "Filters:")
end


local function add_audio(s)
    local r = mp.get_property_native("audio-params")
    -- in case of e.g. lavi-complex there can be no input audio, only output
    if not r then
        r = mp.get_property_native("audio-out-params")
    end
    if not r then
        return
    end

    append(s, "", {prefix=o.nl .. o.nl .. "Audio:", nl="", indent=""})
    append_property(s, "audio-codec", {prefix_sep="", nl="", indent=""})
    local cc = append(s, r["channel-count"], {prefix="Channels:"})
    append(s, r["format"], {prefix="Format:", nl=cc and "" or o.nl})
    append(s, r["samplerate"], {prefix="Sample Rate:", suffix=" Hz"})
    append_property(s, "packet-audio-bitrate", {prefix="Bitrate:", suffix=" kbps"})
    append_filters(s, "af", "Filters:")
end


-- Determine whether ASS formatting shall/can be used and set formatting sequences
local function eval_ass_formatting()
    o.use_ass = o.ass_formatting and has_vo_window()
    if o.use_ass then
        o.nl = o.ass_nl
        o.indent = o.ass_indent
        o.prefix_sep = o.ass_prefix_sep
        o.b1 = o.ass_b1
        o.b0 = o.ass_b0
        o.it1 = o.ass_it1
        o.it0 = o.ass_it0
    else
        o.nl = o.no_ass_nl
        o.indent = o.no_ass_indent
        o.prefix_sep = o.no_ass_prefix_sep
        if not has_ansi() then
            o.b1 = ""
            o.b0 = ""
            o.it1 = ""
            o.it0 = ""
        else
            o.b1 = o.no_ass_b1
            o.b0 = o.no_ass_b0
            o.it1 = o.no_ass_it1
            o.it0 = o.no_ass_it0
        end
    end
end


-- Returns an ASS string with "normal" stats
local function default_stats()
    local stats = {}
    eval_ass_formatting()
    add_header(stats)
    add_file(stats)
    add_video(stats)
    add_audio(stats)
    return table.concat(stats)
end


-- Returns an ASS string with extended VO stats
local function vo_stats()
    local stats = {}
    eval_ass_formatting()
    add_header(stats)
    append_perfdata(stats, true)
    return table.concat(stats)
end

local function opt_time(t)
    if type(t) == type(1.1) then
        return mp.format_time(t)
    end
    return "?"
end

-- Returns an ASS string with stats about the demuxer cache etc.
local function cache_stats()
    local stats = {}

    eval_ass_formatting()
    add_header(stats)
    append(stats, "", {prefix=o.nl .. o.nl .. "Cache info:", nl="", indent=""})

    local info = mp.get_property_native("demuxer-cache-state")
    if info == nil then
        append(stats, "Unavailable.", {})
        return table.concat(stats)
    end

    local a = info["reader-pts"]
    local b = info["cache-end"]

    append(stats, opt_time(a) .. " - " .. opt_time(b), {prefix = "Packet queue:"})

    local r = nil
    if (a ~= nil) and (b ~= nil) then
        r = b - a
    end

    local r_graph = nil
    if not display_timer.oneshot and o.use_ass then
        r_graph = generate_graph(cache_ahead_buf, cache_ahead_buf.pos,
                                 cache_ahead_buf.len, cache_ahead_buf.max,
                                 nil, 0.8, 1)
        r_graph = o.prefix_sep .. r_graph
    end
    append(stats, opt_time(r), {prefix = "Read-ahead:", suffix = r_graph})

    -- These states are not necessarily exclusive. They're about potentially
    -- separate mechanisms, whose states may be decoupled.
    local state = "reading"
    local seek_ts = info["debug-seeking"]
    if seek_ts ~= nil then
        state = "seeking (to " .. mp.format_time(seek_ts) .. ")"
    elseif info["eof"] == true then
        state = "eof"
    elseif info["underrun"] then
        state = "underrun"
    elseif info["idle"]  == true then
        state = "inactive"
    end
    append(stats, state, {prefix = "State:"})

    local total_graph = nil
    if not display_timer.oneshot and o.use_ass then
        total_graph = generate_graph(cache_total_buf, cache_total_buf.pos,
                                     cache_total_buf.len, cache_total_buf.max,
                                     nil, 0.8, 1)
        total_graph = o.prefix_sep .. total_graph
    end
    append(stats, utils.format_bytes_humanized(info["total-bytes"]),
           {prefix = "Total RAM:", suffix = total_graph})
    append(stats, utils.format_bytes_humanized(info["fw-bytes"]),
           {prefix = "Forward RAM:"})

    local fc = info["file-cache-bytes"]
    if fc ~= nil then
        fc = utils.format_bytes_humanized(fc)
    else
        fc = "(disabled)"
    end
    append(stats, fc, {prefix = "Disk cache:"})

    append(stats, info["debug-low-level-seeks"], {prefix = "Media seeks:"})
    append(stats, info["debug-byte-level-seeks"], {prefix = "Stream seeks:"})

    append(stats, "", {prefix=o.nl .. o.nl .. "Ranges:", nl="", indent=""})

    append(stats, info["bof-cached"] and "yes" or "no",
           {prefix = "Start cached:"})
    append(stats, info["eof-cached"] and "yes" or "no",
           {prefix = "End cached:"})

    local ranges = info["seekable-ranges"] or {}
    for n, r in ipairs(ranges) do
        append(stats, mp.format_time(r["start"]) .. " - " ..
                      mp.format_time(r["end"]),
               {prefix = format("Range %s:", n)})
    end

    return table.concat(stats)
end

local function graph_add_value(graph, value)
    graph.pos = (graph.pos % graph.len) + 1
    graph[graph.pos] = value
    graph.max = max(graph.max, value)
end

-- Record 1 sample of cache statistics.
-- (Unlike record_data(), this does not return a function, but runs directly.)
local function record_cache_stats()
    local info = mp.get_property_native("demuxer-cache-state")
    if info == nil then
        return
    end

    local a = info["reader-pts"]
    local b = info["cache-end"]
    if (a ~= nil) and (b ~= nil) then
        graph_add_value(cache_ahead_buf, b - a)
    end

    graph_add_value(cache_total_buf, info["total-bytes"])
end

cache_recorder_timer = mp.add_periodic_timer(0.25, record_cache_stats)
cache_recorder_timer:kill()

-- Current page and <page key>:<page function> mapping
curr_page = o.key_page_1
pages = {
    [o.key_page_1] = { f = default_stats, desc = "Default" },
    [o.key_page_2] = { f = vo_stats, desc = "Extended Frame Timings" },
    [o.key_page_3] = { f = cache_stats, desc = "Cache Statistics" },
}


-- Returns a function to record vsratio/jitter with the specified `skip` value
local function record_data(skip)
    init_buffers()
    skip = max(skip, 0)
    local i = skip
    return function()
        if i < skip then
            i = i + 1
            return
        else
            i = 0
        end

        if o.plot_vsync_jitter then
            local r = mp.get_property_number("vsync-jitter", nil)
            if r then
                vsjitter_buf.pos = (vsjitter_buf.pos % vsjitter_buf.len) + 1
                vsjitter_buf[vsjitter_buf.pos] = r
                vsjitter_buf.max = max(vsjitter_buf.max, r)
            end
        end

        if o.plot_vsync_ratio then
            local r = mp.get_property_number("vsync-ratio", nil)
            if r then
                vsratio_buf.pos = (vsratio_buf.pos % vsratio_buf.len) + 1
                vsratio_buf[vsratio_buf.pos] = r
                vsratio_buf.max = max(vsratio_buf.max, r)
            end
        end
    end
end

-- Call the function for `page` and print it to OSD
local function print_page(page)
    if o.persistent_overlay then
        mp.set_osd_ass(0, 0, pages[page].f())
    else
        mp.osd_message(pages[page].f(), display_timer.oneshot and o.duration or o.redraw_delay + 1)
    end
end


local function clear_screen()
    if o.persistent_overlay then mp.set_osd_ass(0, 0, "") else mp.osd_message("", 0) end
end


-- Add keybindings for every page
local function add_page_bindings()
    local function a(k)
        return function()
            curr_page = k
            print_page(k)
            if display_timer.oneshot then display_timer:kill() ; display_timer:resume() end
        end
    end
    for k, _ in pairs(pages) do
        mp.add_forced_key_binding(k, k, a(k), {repeatable=true})
    end
end


-- Remove keybindings for every page
local function remove_page_bindings()
    for k, _ in pairs(pages) do
        mp.remove_key_binding(k)
    end
end


local function process_key_binding(oneshot)
    -- Stats are already being displayed
    if display_timer:is_enabled() then
        -- Previous and current keys were oneshot -> restart timer
        if display_timer.oneshot and oneshot then
            display_timer:kill()
            print_page(curr_page)
            display_timer:resume()
        -- Previous and current keys were toggling -> end toggling
        elseif not display_timer.oneshot and not oneshot then
            display_timer:kill()
            cache_recorder_timer:stop()
            clear_screen()
            remove_page_bindings()
            if recorder then
                mp.unobserve_property(recorder)
                recorder = nil
            end
        end
    -- No stats are being displayed yet
    else
        if not oneshot and (o.plot_vsync_jitter or o.plot_vsync_ratio) then
            recorder = record_data(o.skip_frames)
            -- Rely on the fact that "vsync-ratio" is updated at the same time.
            -- Using "none" to get a sample any time, even if it does not change.
            -- Will stop working if "vsync-jitter" property change notification
            -- changes, but it's fine for an internal script.
            mp.observe_property("vsync-jitter", "none", recorder)
            cache_recorder_timer:resume()
        end
        display_timer:kill()
        display_timer.oneshot = oneshot
        display_timer.timeout = oneshot and o.duration or o.redraw_delay
        add_page_bindings()
        print_page(curr_page)
        display_timer:resume()
    end
end


-- Create the timer used for redrawing (toggling) or clearing the screen (oneshot)
-- The duration here is not important and always set in process_key_binding()
display_timer = mp.add_periodic_timer(o.duration,
    function()
        if display_timer.oneshot then
            display_timer:kill() ; clear_screen() ; remove_page_bindings()
        else
            print_page(curr_page)
        end
    end)
display_timer:kill()

-- Single invocation key binding
mp.add_key_binding(o.key_oneshot, "display-stats", function() process_key_binding(true) end,
    {repeatable=true})

-- Toggling key binding
mp.add_key_binding(o.key_toggle, "display-stats-toggle", function() process_key_binding(false) end,
    {repeatable=false})

-- Single invocation bindings without key, can be used in input.conf to create
-- bindings for a specific page: "e script-binding stats/display-page-2"
for k, _ in pairs(pages) do
    mp.add_key_binding(nil, "display-page-" .. k, function() process_key_binding(true) end,
        {repeatable=true})
end

-- Reprint stats immediately when VO was reconfigured, only when toggled
mp.register_event("video-reconfig",
    function()
        if display_timer:is_enabled() then
            print_page(curr_page)
        end
    end)
