if not modules then modules = { } end modules ['char-bri'] = {
    version   = 1.001,
    comment   = "companion to char-ini.mkiv",
    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
    copyright = "PRAGMA ADE / ConTeXt Development Team",
    license   = "see context related readme files"
}

-- We use a somewhat indirect approach because we generated the database and
-- have to do that again probably. At some point we can move some to char-def
-- so the interfaces here are kind of private and can change.
--
-- This is just an experiment. The data is taken from Wikipedia and the nemeth
-- sequences come from a 2021 blog by Murray Sargent (from Microsoft):
--
-- https://devblogs.microsoft.com/math-in-office/unicode-math-braille-sequences/

local next = next
local gsub = string.gsub
local utfbyte, utfsplit = utf.byte, string.utfvaluetable
local sortedkeys = table.sortedkeys

local braille      = { }
characters.braille = braille

local codepoints = {
    digits = {
        [48] = "⠚",
        [49] = "⠁",
        [50] = "⠃",
        [51] = "⠉",
        [52] = "⠙",
        [53] = "⠑",
        [54] = "⠋",
        [55] = "⠛",
        [56] = "⠓",
        [57] = "⠊",
    },
    letters = {
        [97] = "⠁",
        [98] = "⠃",
        [99] = "⠉",
       [100] = "⠙",
       [101] = "⠑",
       [102] = "⠋",
       [103] = "⠛",
       [104] = "⠓",
       [105] = "⠊",
       [106] = "⠚",
       [107] = "⠅",
       [108] = "⠇",
       [109] = "⠍",
       [110] = "⠝",
       [111] = "⠕",
       [112] = "⠏",
       [113] = "⠟",
       [114] = "⠗",
       [115] = "⠎",
       [116] = "⠞",
       [117] = "⠥",
       [118] = "⠧",
       [119] = "⠺",
       [120] = "⠭",
       [121] = "⠽",
       [122] = "⠵",
    },
    punctuation = {
        [33] = "⠖",
        [34] = "⠸⠡",
        [40] = "⠐⠣",
        [41] = "⠐⠜",
        [44] = "⠂",
        [45] = "⠤",
        [46] = "⠲",
        [47] = "⠸⠌",
        [58] = "⠒",
        [59] = "⠆",
        [63] = "⠦",
      [8211] = "⠠⠤",
      [8212] = "⠐⠠⠤",
      [8216] = "⠄⠦",
      [8217] = "⠄⠴",
      [8220] = "⠘⠦",
      [8221] = "⠘⠴",
    },
    ueb = {
        [33] = "⠖",
        [34] = "⠠⠶",
        [35] = "⠸⠹",
        [36] = "⠈⠎",
        [37] = "⠨⠴",
        [38] = "⠈⠯",
        [39] = "⠄",
        [40] = "⠐⠣",
        [41] = "⠐⠜",
        [42] = "⠐⠔",
        [43] = "⠐⠖",
        [44] = "⠂",
        [45] = "⠤",
        [46] = "⠼⠲",
        [47] = "⠸⠌",
        [58] = "⠒",
        [59] = "⠆",
        [60] = "⠈⠣",
        [61] = "⠐⠶",
        [62] = "⠈⠜",
        [63] = "⠦",
        [64] = "⠈⠁",
        [91] = "⠨⠣",
        [92] = "⠸⠡",
        [93] = "⠨⠜",
        [94] = "⠈⠢",
        [95] = "⠨⠤",
       [123] = "⠸⠣",
       [124] = "⠸⠳",
       [125] = "⠸⠜",
       [126] = "⠈⠔",
       [162] = "⠈⠉",
       [163] = "⠈⠇",
       [167] = "⠘⠎",
       [169] = "⠘⠉",
       [172] = "⠈⠹",
       [174] = "⠘⠗",
       [176] = "⠘⠚",
       [177] = "⠸⠖",
       [182] = "⠘⠏",
       [215] = "⠐⠦",
       [247] = "⠐⠌",
       [913] = "⠠⠨⠁",
       [914] = "⠠⠨⠃",
       [915] = "⠠⠨⠛",
       [916] = "⠠⠨⠙",
       [917] = "⠠⠨⠑",
       [918] = "⠠⠨⠵",
       [919] = "⠠⠨⠱",
       [920] = "⠠⠨⠹",
       [921] = "⠠⠨⠊",
       [922] = "⠠⠨⠅",
       [923] = "⠠⠨⠇",
       [924] = "⠠⠨⠍",
       [925] = "⠠⠨⠝",
       [926] = "⠠⠨⠭",
       [927] = "⠠⠨⠕",
       [928] = "⠠⠨⠏",
       [929] = "⠠⠨⠗",
       [931] = "⠠⠨⠎",
       [932] = "⠠⠨⠞",
       [933] = "⠠⠨⠥",
       [934] = "⠠⠨⠋",
       [935] = "⠠⠨⠯",
       [936] = "⠠⠨⠽",
       [937] = "⠠⠨⠺",
       [945] = "⠨⠁",
       [946] = "⠨⠃",
       [947] = "⠨⠛",
       [948] = "⠨⠙",
       [949] = "⠨⠑",
       [950] = "⠨⠵",
       [951] = "⠨⠱",
       [952] = "⠨⠹",
       [953] = "⠨⠊",
       [954] = "⠨⠅",
       [955] = "⠨⠇",
       [956] = "⠨⠍",
       [957] = "⠨⠝",
       [958] = "⠨⠭",
       [959] = "⠨⠕",
       [960] = "⠨⠏",
       [961] = "⠨⠗",
       [962] = "⠨⠎",
       [963] = "⠨⠎",
       [964] = "⠨⠞",
       [965] = "⠨⠥",
       [966] = "⠨⠋",
       [967] = "⠨⠯",
       [968] = "⠨⠽",
       [969] = "⠨⠺",
      [8212] = "⠠⠤",
      [8213] = "⠐⠠⠤",
      [8216] = "⠠⠦",
      [8217] = "⠠⠴",
      [8220] = "⠘⠦",
      [8221] = "⠘⠴",
      [8224] = "⠈⠠⠹",
      [8225] = "⠈⠠⠻",
      [8226] = "⠸⠲",
      [8242] = "⠶",
      [8243] = "⠶⠶",
      [8592] = "⠳⠪",
      [8593] = "⠳⠬",
      [8594] = "⠳⠕",
      [8595] = "⠳⠩",
      [8596] = "⠰⠳⠺⠗⠕",
      [8598] = "⠳⠱",
      [8599] = "⠳⠎",
      [8600] = "⠳⠣",
      [8601] = "⠳⠜",
      [8656] = "⠰⠳⠶⠶⠪",
      [8657] = "⠰⠳⠶⠶⠬",
      [8658] = "⠰⠳⠶⠶⠕",
      [8659] = "⠰⠳⠶⠶⠩",
      [8704] = "⠘⠁",
      [8706] = "⠈⠙",
      [8707] = "⠘⠢",
      [8709] = "⠈⠚",
      [8711] = "⠘⠙",
      [8712] = "⠘⠑",
      [8715] = "⠈⠘⠑",
      [8722] = "⠐⠤",
      [8723] = "⠸⠤",
      [8728] = "⠐⠴",
      [8730] = "⠐⠩",
      [8733] = "⠸⠐⠶",
      [8734] = "⠼⠿",
      [8736] = "⠸⠪",
      [8737] = "⠨⠸⠪",
      [8741] = "⠼⠇",
      [8743] = "⠈⠦",
      [8744] = "⠈⠖",
      [8745] = "⠨⠦",
      [8746] = "⠨⠖",
      [8747] = "⠮",
      [8748] = "⠮⠮",
      [8749] = "⠮⠮⠮",
      [8750] = "⠈⠮",
      [8756] = "⠠⠡",
      [8757] = "⠈⠌",
      [8758] = "⠒",
      [8759] = "⠒⠒",
      [8771] = "⠸⠔",
      [8773] = "⠐⠸⠔",
      [8776] = "⠘⠔",
      [8783] = "⠘⠐⠶",
      [8785] = "⠨⠐⠶",
      [8800] = "⠐⠶⠈⠱",
      [8801] = "⠸⠿",
      [8804] = "⠸⠈⠣",
      [8805] = "⠸⠈⠜",
      [8810] = "⠨⠈⠣",
      [8811] = "⠨⠈⠜",
      [8834] = "⠘⠣",
      [8835] = "⠘⠜",
      [8838] = "⠸⠘⠣",
      [8839] = "⠸⠘⠜",
      [8842] = "⠨⠘⠣",
      [8843] = "⠨⠘⠜",
      [8853] = "⠰⠫⠿⠪⠐⠖⠱",
      [8867] = "⠈⠸⠒",
      [8869] = "⠼⠤",
      [8870] = "⠸⠒",
      [8872] = "⠘⠸⠒",
      [8882] = "⠈⠸⠣",
      [8883] = "⠈⠸⠜",
      [8884] = "⠸⠸⠣",
      [8885] = "⠸⠸⠜",
      [8894] = "⠼⠸⠪",
      [8901] = "⠐⠲",
      [9675] = "⠿",
     [10764] = "⠮⠮⠮⠮",
    },
    specials = {
        uppercase = "⠠",
        space     = "⠀",
        number    = "⠼",
        rule      = "⠒",
    },
    alphabets = {
        ["lowercasenormal"]                    = "⠰",
        ["lowercasegreeknormal"]               = "⠨",
        ["lowercasegreekitalic"]               = "⠨⠨",
        ["lowercaseitalic"]                    = "⠨",
        ["lowercasebold"]                      = "⠸",
        ["lowercasebolditalic"]                = "⠸⠨",
        ["lowercasefraktur"]                   = "⠸",
        ["lowercaseboldfraktur"]               = "⠸⠸",
        ["lowercasescript"]                    = "⠈",
        ["lowercaseboldscript"]                = "⠸⠈",
        ["lowercasesansserifnormal"]           = "⠠⠨",
        ["lowercasesansserifitalic"]           = "⠠⠨⠨",
        ["lowercasesansserifbold"]             = "⠠⠨⠸",
        ["lowercasesansserifbolditalic"]       = "⠠⠨⠸⠨",

        ["uppercase"]                          = "⠠",

     -- ["russian"]                            = "⠈⠈",
     -- ["hebrew"]                             = "⠠⠠",
     -- ["altgreek"]                           = "⠨⠈",

     -- ["lowercasedoublestruck"]              = ""
     -- ["lowercasegreekbold"]                 = ""
     -- ["lowercasegreekbolditalic"]           = ""
     -- ["lowercasegreeksansserifbold"]        = ""
     -- ["lowercasegreeksansserifbolditalic"]  = ""
     -- ["lowercasemonospace"]                 = ""
    },
}

braille.codepoints = codepoints

local textunicodes, mathunicodes, textstrings, mathstrings, textlist, mathlist, specials

local function prepare()

    local charblocks  = characters.blocks
    local uccodes     = characters.uccodes

    local letters     = codepoints.letters
    local cspecials   = codepoints.specials
    local uppercase   = cspecials.uppercase
    local number      = cspecials.number
    local space       = cspecials.space
    local rule        = cspecials.rule

    -- filtered from the mentioned blog webpage:

    local nemeth      = table.load(resolvers.find_file("math-brl.lmt")).nemeth
    codepoints.nemeth = nemeth

    -- we let the tex math engine do the spacing but it can become an option:

    for k, v in next, nemeth do
        nemeth[k] = gsub(v,space,"")
    end

    textstrings  = { }
    mathstrings  = { }
    textunicodes = { }
    mathunicodes = { }

    for k, v in next, codepoints.letters do
        textstrings[k] = v
        mathstrings[k] = v
        local K = uccodes[k]
        if K then
            local V = uppercase .. v
            textstrings[K] = V
            mathstrings[K] = V
        end
    end

    for k, v in next, codepoints.digits do
        local d = number .. v
        textstrings[k] = v
        mathstrings[k] = v
    end

    for k, v in next, codepoints.punctuation do
        textstrings[k] = v
        mathstrings[k] = v
    end
    -- overlaps with the above

    for k, v in next, codepoints.ueb do
        textstrings[k] = v
        mathstrings[k] = v
    end

    for k, v in next, codepoints.nemeth do
        mathstrings[k] = v
        if not textstrings[k] then
            textstrings[k] = v
        end
    end

    for k, v in next, codepoints.alphabets do
        local block = charblocks[k]
        if block then
            local c = utfbyte('a')
            for i=block.first,block.last do
                mathstrings[i] = v..letters[c]
                if not textstrings[i] then
                    textstrings[i] = v .. letters[c]
                end
                c = c + 1
            end
        end
    end

    for k, v in next, textstrings do
        textunicodes[k] = utfsplit(v)
    end
    for k, v in next, mathstrings do
        mathunicodes[k] = utfsplit(v)
    end

    textlist = sortedkeys(textstrings)
    mathlist = sortedkeys(mathstrings)

    specials = {
        uppercase = utfbyte(uppercase),
        number    = utfbyte(number),
        space     = utfbyte(space),
        rule      = utfbyte(rule)
    }
end

-- maybe an iterator

function braille.textlist   ()  if not textlist     then prepare() end return textlist        end
function braille.mathlist   ()  if not mathlist     then prepare() end return mathlist        end
function braille.textunicode(n) if not textunicodes then prepare() end return textunicodes[n] end
function braille.mathunicode(n) if not mathunicodes then prepare() end return mathunicodes[n] end
function braille.textstring (n) if not textstrings  then prepare() end return textstrings [n] end
function braille.mathstring (n) if not mathstrings  then prepare() end return mathstrings [n] end
function braille.special    (n) if not specials     then prepare() end return specials    [n] end