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

bool writedata(const char *basename, 
               unsigned int id, 
               const char *data,
               unsigned int dsize) {
    bool status = false;
    char *fn    = (char*)malloc(sizeof(char) * strlen(basename) + 4);
    sprintf(fn, "%s_%d", basename, id);
    FILE *out   = fopen(fn, "w");
    if (out != NULL) {
        fwrite(data, sizeof(char), dsize, out);
        fclose(out);
        status = true;
    }
    free(fn);
    return status;
}

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

        start = ph -> offsets[i];
        // the last offset still has some data until the end of file
        end   = (i == (ph -> numOffset) - 1) ? s : ph -> offsets[i + 1];
        // copy sector to write buffer
        wsize   = end - start;
        printf("end is %x - i is %d - wsize is %x\n", end, i, wsize);
        wbuffer = (char*)malloc(sizeof(char) * wsize);
        memcpy(wbuffer, buffer + start, wsize);
        // create a file.
        writedata(name, i, wbuffer, wsize);
    }
    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, unsigned int *s) {
    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);
    *s = rcnt;
    return buf;
}

int main(int argc, char ** argv) {
    char *filename     = argv[1];
    unsigned int fsize = 0;
    char *filedata     = readpld(filename, &fsize);
    printf("fsize is %i\n", fsize);
    if (filedata != NULL && fsize != 0) {
        struct PldHeader *pldh = read_pldheader(filedata);
        unpackpld(filedata, pldh, filename, fsize);
        free(pldh -> offsets);
        free(pldh);
    }
    free(filedata);
    return 0;
}