#!/usr/bin/env ruby
#   Copyright (c) 2016 Ray Chason
#   NetHack may be freely redistributed.  See license for details.

# Information about a single glyph in the font
class Glyph

    attr :width
    attr :height
    attr_accessor :bytes
    attr_accessor :code

    def initialize(width, height)
        @width = width
        @height = height
        @bytes = ""
        @code = []
        bwidth = (width + 7) / 8
    end

end

# This converts an unsigned integer to four little endian bytes
def write_u32(x)
    ([ x, (x >> 8), (x >> 16), (x >> 24) ].map {|x|
        (x & 0xFF).chr(Encoding::ASCII_8BIT)
    }).join('')
end

# IBM437 order as NetHack expects
ibm437 = [
    0x0000, 0x263A, 0x263B, 0x2665, 0x2666, 0x2663, 0x2660, 0x2022,
    0x25D8, 0x25CB, 0x25D9, 0x2642, 0x2640, 0x266A, 0x266B, 0x263C,
    0x25BA, 0x25C4, 0x2195, 0x203C, 0x00B6, 0x00A7, 0x25AC, 0x21A8,
    0x2191, 0x2193, 0x2192, 0x2190, 0x221F, 0x2194, 0x25B2, 0x25BC,
    0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027,
    0x0028, 0x0029, 0x002A, 0x002B, 0x002C, 0x002D, 0x002E, 0x002F,
    0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037,
    0x0038, 0x0039, 0x003A, 0x003B, 0x003C, 0x003D, 0x003E, 0x003F,
    0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047,
    0x0048, 0x0049, 0x004A, 0x004B, 0x004C, 0x004D, 0x004E, 0x004F,
    0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057,
    0x0058, 0x0059, 0x005A, 0x005B, 0x005C, 0x005D, 0x005E, 0x005F,
    0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067,
    0x0068, 0x0069, 0x006A, 0x006B, 0x006C, 0x006D, 0x006E, 0x006F,
    0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077,
    0x0078, 0x0079, 0x007A, 0x007B, 0x007C, 0x007D, 0x007E, 0x2302,
    0x00C7, 0x00FC, 0x00E9, 0x00E2, 0x00E4, 0x00E0, 0x00E5, 0x00E7,
    0x00EA, 0x00EB, 0x00E8, 0x00EF, 0x00EE, 0x00EC, 0x00C4, 0x00C5,
    0x00C9, 0x00E6, 0x00C6, 0x00F4, 0x00F6, 0x00F2, 0x00FB, 0x00F9,
    0x00FF, 0x00D6, 0x00DC, 0x00A2, 0x00A3, 0x00A5, 0x20A7, 0x0192,
    0x00E1, 0x00ED, 0x00F3, 0x00FA, 0x00F1, 0x00D1, 0x00AA, 0x00BA,
    0x00BF, 0x2310, 0x00AC, 0x00BD, 0x00BC, 0x00A1, 0x00AB, 0x00BB,
    0x2591, 0x2592, 0x2593, 0x2502, 0x2524, 0x2561, 0x2562, 0x2556,
    0x2555, 0x2563, 0x2551, 0x2557, 0x255D, 0x255C, 0x255B, 0x2510,
    0x2514, 0x2534, 0x252C, 0x251C, 0x2500, 0x253C, 0x255E, 0x255F,
    0x255A, 0x2554, 0x2569, 0x2566, 0x2560, 0x2550, 0x256C, 0x2567,
    0x2568, 0x2564, 0x2565, 0x2559, 0x2558, 0x2552, 0x2553, 0x256B,
    0x256A, 0x2518, 0x250C, 0x2588, 0x2584, 0x258C, 0x2590, 0x2580,
    0x03B1, 0x00DF, 0x0393, 0x03C0, 0x03A3, 0x03C3, 0x00B5, 0x03C4,
    0x03A6, 0x0398, 0x03A9, 0x03B4, 0x221E, 0x03C6, 0x03B5, 0x2229,
    0x2261, 0x00B1, 0x2265, 0x2264, 0x2320, 0x2321, 0x00F7, 0x2248,
    0x00B0, 0x2219, 0x00B7, 0x221A, 0x207F, 0x00B2, 0x25A0, 0x00A0,
]

# As ibm437, but mapping Unicode back to the IBM437 position
ibm437_rev = {}
ibm437.size.times {|i| ibm437_rev[ibm437[i]] = i}

# Variables to be used in the main loop
font = [ nil ] * ibm437.size # Font position to glyph
font_by_bytes = {}           # Bitmap string to font position
font_by_code = {}            # Unicode code point to glyph
width = nil
height = nil
bwidth = nil
glyph = nil
bitmap = false
row = 0

if ARGV.size != 2 then
  	STDERR.puts "Usage: #{$0} <input-bdf> <output-psf>"
    exit 1
end

File.foreach(ARGV[0]) do |line|
    line.chomp!
    if line.start_with?('FONTBOUNDINGBOX ') then
        # Width and height of a glyph
        rec = line.split
        width = rec[1].to_i
        height = rec[2].to_i
        bwidth = (width + 7) / 8
    elsif line.start_with?('STARTCHAR ') then
        # A glyph begins here
        glyph = Glyph.new(width, height)
    elsif line.start_with?('ENCODING ') then
        # This line provides the Unicode code point
        rec = line.split
        glyph.code << rec[1].to_i
    elsif line.start_with?('BITMAP') then
        # Bitmap data appears on following lines
        bitmap = true
        row = 0
    elsif line.start_with?('ENDCHAR') then
        # End of bitmap data
        # Position will be according to IBM437 if the code point is in IBM437,
        # else matching any prior occurrence if the same glyph has appeared
        # before, else as a new glyph
        pos = ibm437_rev[glyph.code[0]] || font_by_bytes[glyph.bytes] || font.size
        if font[pos].nil? then
            font[pos] = glyph
            font_by_bytes[glyph.bytes] = pos
        else
            font[pos].code.concat(glyph.code)
        end
        font_by_code[glyph.code[0]] = pos
        glyph = nil
        bitmap = false
    elsif bitmap then
        # Hex data after BITMAP and before ENDCHAR
        bwidth.times do |col|
            byte = line[col*2..col*2+1].to_i(16).chr(Encoding::ASCII_8BIT)
            glyph.bytes << byte
        end
        row += 1
    end
end

# The provided BDFs code positions 16 and 17 differently from what NetHack
# expects
if font[ibm437_rev[0x25BA]].nil? and not font_by_code[0x25B6].nil? then
    pos1 = font_by_code[0x25B6]
    pos2 = ibm437_rev[0x25BA]
    font[pos2] = font[pos1]
    font[pos2].code << 0x25BA
    font[pos1] = nil
end
if font[ibm437_rev[0x25C4]].nil? and not font_by_code[0x25C0].nil? then
    pos1 = font_by_code[0x25C0]
    pos2 = ibm437_rev[0x25C4]
    font[pos2] = font[pos1]
    font[pos2].code << 0x25C4
    font[pos1] = nil
end

# Fill any empty slots; warn if within first 256
i = 0
while i < font.size do
    if font[i].nil? then
        puts "Position #{i} is empty" if i < ibm437.size
        font[i] = font.pop
    end
    i += 1
end

File.open(ARGV[1], "wb") do |outfile|

    # Write the PSF header
    outfile.write("\x72\xB5\x4A\x86")           # magic
    outfile.write(write_u32(0))                 # version
    outfile.write(write_u32(32))                # headersize
    outfile.write(write_u32(0x01))              # flags (Unicode table present)
    outfile.write(write_u32(font.size))         # length
    outfile.write(write_u32(bwidth * height))   # charsize
    outfile.write(write_u32(height))            # height
    outfile.write(write_u32(width))             # width

    # Write the glyphs
    font.each {|glyph| outfile.write(glyph.bytes)}

    # Write the Unicode mappings
    font.each do |glyph|
        outfile.write((glyph.code.map {|x| x.chr(Encoding::UTF_8)}).join(''))
        outfile.write(0xFF.chr(Encoding::ASCII_8BIT))
    end
end