const std = @import("std");

pub const Psf2Header = extern struct {
    magic: u32 = 0x864ab572,
    version: u32,
    header_size: u32,
    flags: u32,
    numglyph: u32,
    bytes_per_glyph: u32,
    height: u32,
    width: u32,

    pub fn bytesPerLine(self: *const Psf2Header) u32 {
        return (self.width + 7) / 8;
    }
};

pub const Font = struct {
    const Self = @This();
    fontdata: []const u8 align(4),
    pub fn new(fontdata: []const u8) Self {
        return .{
            .fontdata = fontdata,
        };
    }

    pub fn getHdr(self: *const Self) *const Psf2Header {
        return @ptrCast(@alignCast(self.fontdata));
    }

    pub fn getGlyph(self: *const Self, ch: u8) ![]const u8 {
        const hdr = self.getHdr();
        const startpos: u64 = @as(u64, hdr.header_size) + @as(u64, ch) * @as(u64, hdr.bytes_per_glyph);

        if (self.fontdata.len < startpos + @as(u64, hdr.bytes_per_glyph)) return error.InvalidCharacter;

        return self.fontdata[startpos..][0..hdr.bytes_per_glyph];
    }
};