local posix = require("posix")

local function time()
    if posix then
        local s, ns = posix.clock_gettime()
        return s + ns / 10^9
    else
        return os.time()
    end
end

--[[
    show progress thru a review session, conditioned on the user
    configuring that to happen
]]
local function showprogress(k, n, conf)
    if conf:get("ShowProgress") and conf:get("ShowProgress") ~= "false" then
        io.write(string.format("(%d/%d) ", k, n))
    end
end

--[[
    display text with images, inserted with `IMG[path]`
    implementation may be platform-specific
    `basepath` points to the base directory of the images
]]
local function imgify(text, basepath, ind, climn, conf, question)
    local fh = io.popen("tput lines")
    local tl = tonumber(fh:read("a"))
    fh:close()
    io.write(("\n"):rep(math.floor(0.4 * tl)))
    local pt = text:gsub(IMG_PATTERN, "")
    showprogress(ind, climn, conf)
    if conf:get("BoldContext") then
        local csi, cei = pt:find("^[^:]+:")
        if csi then
            local cpt = pt:sub(csi, cei)
            io.write("\x1b[1m")
            io.write(cpt)
            io.write("\x1b[0m")
            pt = pt:sub(cei + 1)
            if question then
                io.flush()
                os.execute("sleep 0.3")
            end
        end
    end
    io.write(pt)
    local ifl = {}
    for p in text:gmatch(IMG_PATTERN) do
        table.insert(ifl, 1, basepath .. p)
    end
    -- Linux/dwm
    if #ifl > 0 then
        os.execute(string.format(
            "/usr/local/bin/iv -t '%s' %s &",
            pt:gsub("\n", " "):gsub("'", "\""):gsub("\x1b[^m]+m", ""), table.concat(ifl, " ")
        ))
    end
end

--[[
    rounds `x` to `n` places (default 0) after the radix point
    in base `b` (default 10)
]]
local function round(x, n, b)
    local b = b or 10
    local n = n or 0
    if n == 0 then
        return math.tointeger(math.floor(x * b ^ n) / b ^ n)
    else
        return math.floor(x * b ^ n) / b ^ n
    end
end

--[[
    return human-friendly string to present a duration (input in seconds),
    e.g. "44:37", "4.8h", "11d", "8.3m", "17.4y"
]]
local function disptime(ts)
    local YDAY = 365.24
    local MDAY = YDAY / 12
    local DSEC = 86400
    local HSEC = 3600
    if ts >= 3 * YDAY * DSEC then
        return round(ts / (YDAY * DSEC), 1) .. "y"
    elseif ts >= 4 * MDAY * DSEC then
        return round(ts / (MDAY * DSEC), 1) .. "m"
    elseif ts >= 10 * DSEC then
        return round(ts / DSEC) .. "d"
    elseif ts >= 1.5 * DSEC then
        return round(ts / DSEC, 1) .. "d"
    elseif ts >= 8 * HSEC then
        return round(ts / HSEC) .. "h"
    elseif ts >= HSEC then
        return round(ts / HSEC, 1) .. "h"
    else
        return string.format("%d:%02d", round(ts / 60), round(ts % 60))
    end
end

local function fn(config, deck, deckfname)
    if not isatty() then
        io.write("Review should be done in the terminal\n")
        return nil
    end
    -- collect list of index-pairs for prompts to be reviewed this session
    local ctrt = review.list(deck, config)
    io.write(string.format(
        "%d prompts are ready for review.\nHow many to review in this session? ", #ctrt
    ))
    io.flush()
    local climt = io.read("l")
    local climn = tonumber(climt)
    if not climn then
        io.write("Input not a number; aborting\n")
        return nil
    end
    climn = math.min(climn, #ctrt)
    local lrc = 0
    local editqueue = {}
    local start = time()
    local rt = {}
    -- review prompts in this session's set
    for ind, ip in ipairs(ctrt) do
        if ind > climn then
            break
        end
        local pr = deck[ip[1]].pr[ip[2]]
        local pst = pr:text()
        local st = time()
        imgify(pst:gsub("%%A", "___"), deckfname:match(".*/") or "", ind, climn, config, true)
        io.write("\n")
        table.insert(rt, time())
        io.read("l")
        rt[#rt] = time() - rt[#rt]
        clear()
        imgify(
            pst:gsub("%%A", "\x1b[1m" .. (pr:ans():gsub("%%", "%%%%")) .. "\x1b[0m"),
            deckfname:match(".*/") or "",
            ind,
            climn,
            config,
            false
        )
        io.write(string.format(
            "\nAgain / Hard (%s) / Good (%s) / Easy (%s) / Correction ",
            disptime(review.schedule(pr, st, 0.5, config)),
            disptime(review.schedule(pr, st, 1, config)),
            disptime(review.schedule(pr, st, 1.5, config))
        ))
        io.flush()
        local resp = io.read("l")
        local sc = review.succfromstr(resp)
        if sc == -1 then
            table.insert(editqueue, ip)
        else
            if sc == 0 then
                lrc = lrc + 1
            end
            review.update(deck[ip[1]].pr[ip[2]], st, sc, config)
        end
        clear()
        if resp:sub(#resp):lower() == "q" then
            climn = ind
            break
        end
    end
    if #ctrt > 0 then
        local acr = math.min(#ctrt, climn)
        local endt = time()
        io.write(string.format(
            "Reviewed %d prompts in %f seconds\n",
            acr, endt - start
        ))
        local s
        if lrc == 1 then s = "" else s = "s" end
        io.write(string.format(
            "(%d lapse%s, %f seconds per card)\n",
            lrc, s, (endt - start) / acr
        ))
        local trt = 0
        for _, x in ipairs(rt) do
            trt = trt + x
        end
        io.write(string.format(
            "Average %f seconds for recall per card\n",
            trt / acr
        ))
    end
    if #editqueue > 0 then
        io.write(string.format("The following cards are marked for correction:\n"))
        for _, ip in ipairs(editqueue) do
            io.write(string.format("%d %s\n", ip[1], deck[ip[1]]))
        end
    end
    if climn > 0 then
        return deck
    end
end

return { desc = "(r)eview sesion", nd = true, fn = fn }