#include "devil1pld.h"
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void unpackpld(const char *buffer, 
               const struct PldHeader *ph, 
               const char *name) {
    char *wbuffer      = NULL; // write buffer that will change.
    unsigned int wsize = 0;    // size of wbuffer.
    unsigned int i;
    for (i = 0; (i + 1) < (ph -> numOffset); i++) {
        printf("start: %x - end: %x\n", 
            ph -> offsets[i], 
            ph -> offsets[i + 1]);

        // copy sector to write buffer
        wsize   = (ph -> offsets[i + 1]) - (ph -> offsets[i]) + 1;
        wbuffer = (char*)malloc(sizeof(char) * wsize);
        memcpy(wbuffer, buffer + (ph -> offsets[i]), wsize);
        // create a file.
        char *fn = (char*)malloc(sizeof(char)*strlen(name) + 4);
        sprintf(fn, "%s_%d", name, i);
        FILE *out  = fopen(fn, "w");
        fputs(wbuffer, out);
        fclose(out);
        free(fn);
    }
    free(wbuffer);
}

void show_pldheader(struct PldHeader *x) {
    printf("number of offsets = %i\n", x -> numOffset);
    unsigned int i;
    for (i = 0; i < x -> numOffset; i++) {
        printf("offset %i = %x\n", i, x -> offsets[i]);
    }
}

struct PldHeader *read_pldheader(const char *buffer) {
    if (buffer == NULL) {
        return NULL;
    }
    int32_t *n                = (int32_t*)buffer;
    struct PldHeader *ph      = (struct PldHeader*)malloc(
        sizeof(struct PldHeader)
    );   
    uint32_t size_offsets = sizeof(uint32_t) * n[0];
    ph -> offsets         = (uint32_t*)malloc(size_offsets);
    if (ph -> offsets == NULL) {
        perror("Error 4: ");
        free(ph);
        free(ph -> offsets);
        return NULL;
    }
    // set data of struct.
    ph -> numOffset = n[0];
    memcpy(ph -> offsets, buffer + sizeof(int32_t), size_offsets);
    return ph;
}

char *readpld(const char *fname) {
    FILE *f           = fopen(fname, "rb");
    unsigned int size = 0; // number of elements to buffer;
    unsigned int rcnt = 0; // number of char's read by fread(...)
    if (f == NULL) {
        perror("Error 1: ");
        return NULL;
    }
    // this method of determining file size doesn't work until 2 GB.
    fseek(f, 0, SEEK_END);
    size = ftell(f);
    rewind(f);
    char *buf = (char*)malloc(sizeof(char) * size);
    if (buf == NULL) {
        perror("Error 2: ");
        free(buf);
        return NULL;
    }
    rcnt = fread(buf, sizeof(char), size, f);
    if (rcnt < size) {
        perror("Error 3: ");
        free(buf);
        return NULL;
    }
    fclose(f);
    return buf;
}

int main(int argc, char ** argv) {
    char *filename  = argv[1];
    char *filedata  = readpld(filename);
    if (filedata != NULL) {
        struct PldHeader *pldh = read_pldheader(filedata);
        unpackpld(filedata, pldh, filename);
        free(pldh -> offsets);
        free(pldh);
    }
    free(filedata);
    return 0;
}