// Parses a dies irae "script" extracted from memory and dumps the content text

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#define and &&
#define or ||

#ifndef NULL
#define NULL 0
#endif

int fgetc_or_die(FILE * a)
{
    int got = fgetc(a);
    if(feof(a) or ferror(a) or got < 0x00 or got > 0xFF) exit(0);
    return got;
}

FILE * script;
FILE * text;
uint32_t data;

void push(uint32_t codepoint)
{
    if(codepoint == 0xFFFFFFFF) return;

    if(codepoint < 0x20 and codepoint != 0x0D and codepoint != 0x0A)
        fprintf(stderr, "Tried to output a control character %08X\n", (unsigned int)ftell(script)), exit(0);
    if(codepoint < 0x80)
    {
        putc(codepoint&0xFF, text);
    }
    else if(codepoint < 0x800)
    {
        putc(((codepoint&(0x1F<<6))>>6)|0xC0,text);
        putc(((codepoint&(0x3F<<0))>>0)|0x80,text);
    }
    else if(codepoint < 0x10000)
    {
        putc(((codepoint&(0x0F<<12))>>12)|0xE0,text);
        putc(((codepoint&(0x3F<< 6))>> 6)|0x80,text);
        putc(((codepoint&(0x3F<< 0))>> 0)|0x80,text);
    }
    else if(codepoint < 0x110000)
    {
        putc(((codepoint&(0x07<<18))>>18)|0xF0,text);
        putc(((codepoint&(0x3F<<12))>>12)|0x80,text);
        putc(((codepoint&(0x3F<< 6))>> 6)|0x80,text);
        putc(((codepoint&(0x3F<< 0))>> 0)|0x80,text);
    }
}

uint32_t get_codepoint(FILE * file)
{
    data = 0;
    #define CONT()\
    {\
        value <<= 6;\
        int byte = fgetc_or_die(file);\
        if(byte < 0x80 or byte >= 0xC0)\
            printf("Invalid continuation byte at %08X in input\n", (unsigned int)ftell(file)-1), fflush(stderr), exit(0);\
        value |= byte&0x3F;\
    }
    uint32_t value = 0;
    int init = fgetc_or_die(file);

    if(init == 0x06)
    // unknown but is a prefix to another codepoint
    // FIXME: Values other than 0 (which is a pagefeed) should be encoded properly!
    {
        value = get_codepoint(file);
        if(value == 0)
        {
            push(0x0A);
            push(0x0A);
            return 0xFFFFFFFF;
        }
        else
            return 0xFFFFFFFF;
    }

    if(init < 0 or init > 0xFF)
        puts("File over"), fflush(stderr), exit(0);
    else if(init < 0x80)
    {
        value = init;
    }
    else if(init < 0xC0 or init == 0xC0 or init == 0xC1 or init == 0xF5 or init == 0xF6 or init == 0xF7)
        fprintf(stderr, "Invalid initial byte %02X at %08X in input\n", init, (unsigned int)ftell(file)-1), fflush(stderr), exit(0);
    else if(init < 0xE0)
    {
        value |= init&0x1F;
        if(value == 0)
            fprintf(stderr, "Overlong encoding near %08X in input\n", (unsigned int)ftell(file)-1), fflush(stderr), exit(0);
        CONT()
    }
    else if(init < 0xF0)
    {
        value |= init&0x0F;
        if(value == 0)
            fprintf(stderr, "Overlong encoding near %08X in input\n", (unsigned int)ftell(file)-1), fflush(stderr), exit(0);
        CONT()
        CONT()
    }
    else
    {
        value |= init&0x07;
        if(value == 0)
            fprintf(stderr, "Overlong encoding near %08X in input\n", (unsigned int)ftell(file)-1), fflush(stderr), exit(0);
        CONT()
        CONT()
        CONT()
    }
    if(value > 0x10FFFF or (value > 0xD800 and value <= 0xDFFF))
        fprintf(stderr, "Invalid codepoint constrcted near %08X in input\n", (unsigned int)ftell(file)-1), fflush(stderr), exit(0);
    return value;
}

void pull()
{
    data = get_codepoint(script);
}

int main(int argc, char ** argv)
{
    if(argc < 2) return puts("no input given"), 0;

    script = fopen(argv[1], "rb");
    if(!script) return puts("failed to open input"), 0;

    text = stdout;

    while(1)
    {
        pull();
        if(data == 0x01) // furigana
        {
            push(0x3008);
            while(1)
            {
                pull();
                //if(data == 0x0A) break;
                if(data >= 0x20)
                    push(data);
                else break;
            }
            push(0x3009);
            push(0x300A);
            while(1)
            {
                pull();
                if(data >= 0x20 or data == 0x0A)
                    push(data);
                else break;
            }
            push(0x300B);
        }
        else if(data == 0x08) // audio filename is not content text, skip
        {
            while(1)
            {
                pull();
                if(data == 0x00) break;
            }
        }
        else if(data < 0x20)
        {
            if(data == 0x0A or data == 0x0D)
            {
                push(data);
            }
        }
        else
        {
            push(data);
        }
    }
}