OCBF

local unicode = require("unicode")
local fs = require("filesystem")

local charpattern = utf8 and utf8.charpattern or "[\0-\x7F\xC2-\xF4][\x80-\xBF]*"

local function readstr(f)
  local count, reason = f:read(1)
  if not count then return nil, reason or "unexpected EOF" end

  count = string.unpack(">B", count)
  local data, reason = f:read(count)
  if not data or #data ~= count then return nil, reason or "unexpected EOF" end

  return data
end

local function readchr(f)
  local c1, reason = f:read(1)
  if not c1 then return nil, reason or "unexpected EOF" end

  local ctr, c = -1, math.max(c1:byte(), 128)

  repeat
    ctr = ctr + 1
    c = (c - 128) * 2
  until c < 128

  local crest, reason = f:read(ctr)
  if not crest or #crest ~= ctr then return nil, reason or "unexpected EOF" end

  return c1 .. crest
end

local fontBase = {}
fontBase.__index = fontBase

local function loadOCBF(path)
  local font = setmetatable({sizes = {}}, fontBase)

  local f, reason = io.open(path, "rb")
  if not f then return nil, reason end

  if f:read(4) ~= "ocbf" then return nil, "bad signature" end

  font.family, reason = readstr(f)
  if not font.family then return nil, reason end

  font.style, reason = readstr(f)
  if not font.style then return nil, reason end

  while true do
    local char = readchr(f)
    if not char then break end

    local sizewidth, reason = f:read(2)
    if not sizewidth or #sizewidth ~= 2 then
      return nil, reason or "unexpected EOF"
    end

    local size, width = string.unpack(">BB", sizewidth)
    local len = math.ceil(size * width / 8)

    local data = f:read(len)
    if not data or #data ~= len then return nil, reason or "unexpected EOF" end

    if not font.sizes[size] then font.sizes[size] = {} end
    font.sizes[size][char] = {}
    font.sizes[size][char] = {width = width, data = data}
  end

  f:close()
  return font
end

function fontBase:drawChar(set, size, char, x, y)
  checkArg(1, set, "function")
  checkArg(2, size, "number")
  checkArg(3, char, "string")
  checkArg(4, x, "number")
  checkArg(5, y, "number")

  if not self.sizes[size] then
    error("no " .. tostring(size) .. " size in ocbf font", 2)
  end

  local char = self.sizes[size][char]
  local i = 0

  for by = 0, size - 1 do
    for bx = 0, char.width - 1 do
      local bytei = math.floor((by * char.width + bx) / 8)
      local biti = 7 - (by * char.width + bx) % 8
      local byte = string.byte(char.data:sub(bytei + 1, bytei + 1))

      if byte >> biti & 1 == 1 then
        set(bx + x, by + y, 1)
      else
        set(bx + x, by + y, 0)
      end
      i = i + 1
    end
  end
end

function fontBase:draw(set, size, str, x, y)
  checkArg(1, set, "function")
  checkArg(2, size, "number")
  checkArg(3, str, "string")
  checkArg(4, x, "number")
  checkArg(5, y, "number")

  if not self.sizes[size] then
    error("no " .. tostring(size) .. " size in ocbf font", 2)
  end

  local ix = x
  for i = 1, unicode.len(str) do
    local char = unicode.sub(str, i, i)
    if char == "\n" then
      x = ix
      y = y + size
    else
      self:drawChar(set, size, char, x, y)
      x = x + self.sizes[size][char].width
    end
  end
end

function fontBase:width(size, str)
  checkArg(1, size, "number")
  checkArg(2, str, "string")

  local width = 0

  for i = 1, unicode.len(str) do
    local char = unicode.sub(str, i, i)
    width = width + self.sizes[size][char].width
  end

  return width
end

function fontBase:__tostring()
  local out = "font: " .. self.family .. " " .. self.style .. " ["
  local i = 1

  for size in pairs(self.sizes) do
    out = out .. (i == 1 and "" or ", ") .. tostring(size)
    i = i + 1
  end

  return out .. "]"
end

local ocbf = {}

ocbf.path = "/usr/share/fonts:/home/.fonts:."

function ocbf.load(family, style)
  checkArg(1, family, "string")
  checkArg(2, style, "string", "nil")

  local path

  if family:sub(-5, -1) == "ocbf" then
    path = family
  else
    path = ocbf.search(family, style)
  end

  if not path then return nil end

  return loadOCBF(path)
end

function ocbf.search(family, style)
  checkArg(1, family, "string")
  checkArg(2, style, "string")

  for path in ocbf.path:gmatch("[^:]+") do
    path = fs.concat(path, family, style .. ".ocbf")
    if fs.exists(path) then
      return path
    end
  end
end

return ocbf