product listview rendering in c (WIP)

loveos_render.c

// This file is part of the "LoveOS" project
//   (c) 2013 DaWanda GmbH, Paul Asmuth <paul@paulasmuth.com>, et al.
//   All rights reserved.

#include "plv.h"
#include "ruby.h"

VALUE loveos_render = Qnil;

// glue code to call the plv_load_json + plv_render methods from ruby
VALUE method_render_product_listview_from_json(VALUE self, VALUE json, VALUE lang) {
  VALUE     res;
  char*     buf;
  plv_data* plv;

  if (rb_type(json) != RUBY_T_STRING) {
    rb_raise(rb_eTypeError, "first argument (json) must be a string");
    return 0;
  }

  if (rb_type(lang) != RUBY_T_STRING) {
    rb_raise(rb_eTypeError, "second argument (lang) must be a string");
    return 0;
  }

  plv = calloc(1, sizeof(plv_data));

  if (!plv_load_json(plv, RSTRING_PTR(json), RSTRING_PTR(lang))) {
    rb_raise(rb_eRuntimeError, "error loading product_listview JSON, invalid structure?");
    free(plv);
    return 1;
  }

  buf = plv_render(plv);
  res = rb_str_new2(buf);

  free(buf);
  free(plv);

  return res;
}

void Init_loveos_render() {
  loveos_render = rb_define_module("NativeRender");

  rb_define_method(loveos_render, "render_product_listview_from_json", 
    method_render_product_listview_from_json, 2);
}

plv.c

// This file is part of the "LoveOS" project
//   (c) 2013 DaWanda GmbH, Paul Asmuth <paul@paulasmuth.com>, et al.
//   All rights reserved.

#include "plv.h"

#include <stdio.h>
#include <stdlib.h>
#include <jansson.h>
#include <string.h>

// loads a product_listview json blob (from sqltap) into the plv struct
// returns 0 on error, 1 on success
int plv_load_json(plv_data* plv, char* json, char* lang) {
  json_t *root, *product, *images, *image, *user, *shop, *translations;
  json_error_t error;

  if (!(root = json_loads(json, 0, &error)))
    return PLV_LOAD_ERROR;

  if (!json_is_object(root))
    goto error;

  if (!(product = json_object_get(root, "product")))
    goto error;

  if (!(user = json_object_get(product, "user")))
    goto error;

  if (!(shop = json_object_get(user, "shop")))
    goto error;

  if (!(images = json_object_get(product, "images")))
    goto error;

  if (!(translations = json_object_get(product, "translations")))
    goto error;

  if (!json_is_array(images))
    goto error;

  if (!json_is_array(translations))
    goto error;

  if (!(image = json_array_get(images, 0)))
    goto error;

  plv_load_json_attr(product, plv->id,    "id");
  plv_load_json_attr(product, plv->slug,  "slug");
  plv_load_json_attr(product, plv->cents, "cents");
  plv_load_json_attr(image,   plv->image_filename, "filename");
  plv_load_json_attr(shop,    plv->shop_name, "subdomain");
  plv_load_json_attr(product, plv->price_unit, "unit");
  plv_load_json_attr(product, plv->cents, "cents");
  plv_load_json_attr(product, plv->currency, "currency");
  plv_load_json_attr(product, plv->price_milli_units_per_item,
    "milli_units_per_item");

  plv_load_json_translations(plv, translations, lang);

  json_decref(root);
  return PLV_LOAD_SUCCESS;

  error:

  json_decref(root);
  return PLV_LOAD_ERROR;
}

// it ain't pretty but its fast... remember to free the return value
// after use (!)
char* plv_render(plv_data* plv) {
  size_t buf_size = sizeof(plv_data) + 4096;
  char*  buf = calloc(1, buf_size);

  plv_prepare(plv);

  // oh yeah, we can render the listview with one big printf ;)
  snprintf(buf, buf_size, PLV_TEMPLATE,
    plv->url,
    plv->image_url,
    plv->url,
    plv->title,
    plv->shop_name,
    plv->shop_name,
    plv->price_milli_units_per_item,
    plv->price_unit,
    plv->price / 100.0,
    plv->currency
  );

  return buf;
}

void plv_prepare(plv_data* plv) {
  char s3_folder_id_str[16] = "\0";

  // prepare id and price
  plv->id_int = atoi(plv->id);
  plv->price  = atoi(plv->cents);

  // prepare product url
  snprintf(plv->url, PLV_ATTR_SIZE, "/product/%s-%s",
    plv->id, plv->slug);

  // prepare image url
  if ((plv->id_int / PLV_S3_MAX_ID + 1) > 1)
    snprintf(s3_folder_id_str, 16, "%i", plv->id_int / PLV_S3_MAX_ID + 1);

  snprintf(plv->image_url, PLV_ATTR_SIZE, "http://%s/Product%s/%i/%i/listview/%s",
    PLV_S3_HOST,
    s3_folder_id_str,
    plv->id_int / 1000,
    plv->id_int,
    plv->image_filename
  );

  // prepare product title

}

void plv_render_string(char** buf, const char* str) {
  strncpy(*buf, str, PLV_ATTR_SIZE);
  *buf += strlen(str);
}

void plv_load_json_attr(json_t* base, char* dst, const char* attr) {
  json_t* tmp = json_object_get(base, attr);

  if (json_is_string(tmp))
    strncpy(dst, json_string_value(tmp), PLV_ATTR_SIZE);
}

void plv_load_json_translations(plv_data* plv, json_t* translations, char* lang) {
  json_t *translation, *tmp;
  int n;

  for (n = (int) json_array_size(translations); n > 0; n--) {
    translation = json_array_get(translations, n - 1);
    tmp = json_object_get(translation, "attribute");

    if (strcmp(json_string_value(tmp), "title"))
      continue;

    tmp = json_object_get(translation, "text");

    if (json_is_string(tmp))
      strncpy(plv->title, json_string_value(tmp), PLV_ATTR_SIZE);

    tmp = json_object_get(translation, "language");

    if (!strcmp(json_string_value(tmp), lang))
      break;
  }
}

plv.h

// This file is part of the "LoveOS" project
//   (c) 2013 DaWanda GmbH, Paul Asmuth <paul@paulasmuth.com>, et al.
//   All rights reserved.

#ifndef PLV_H
#define PLV_H
#include <jansson.h>

#define PLV_ATTR_SIZE 1024
#define PLV_LOAD_ERROR 0
#define PLV_LOAD_SUCCESS 1
#define PLV_S3_HOST "dawandaimages.s3.amazonaws.com"
#define PLV_S3_MAX_ID 31991150

#define PLV_TEMPLATE \
    "<li>\
      <article class='product'>\
        <a href='#pin' class='product-pin-action'>pin this product</a>\
        <a href='%s' class='product-pic'>\
          <img src='%s' />\
          <a href='%s' class='product-title'>%s</a>\
          <a href='/shop/%s' class='product-shop'>%s</a>\
          <section class='price discounted converted has-pp'\
            data-milli-units-per-item='%s' data-unit='%s'>%.2f %s</section>\
        </a>\
      </article>\
    </li>"

typedef struct {
  char   id[PLV_ATTR_SIZE];
  int    id_int;
  char   slug[PLV_ATTR_SIZE];
  char   url[PLV_ATTR_SIZE];
  char   image_url[PLV_ATTR_SIZE];
  char   image_filename[PLV_ATTR_SIZE];
  char   title[PLV_ATTR_SIZE];
  char   shop_name[PLV_ATTR_SIZE];
  char   cents[PLV_ATTR_SIZE];
  char   currency[PLV_ATTR_SIZE];
  int    price;
  char   price_milli_units_per_item[PLV_ATTR_SIZE];
  char   price_unit[PLV_ATTR_SIZE];
} plv_data;

int plv_load_json(plv_data* plv, char* json, char* lang);
void plv_load_json_attr(json_t* base, char* dst, const char* attr);
void plv_load_json_translations(plv_data* plv, json_t* translations, char* lang);
char* plv_render(plv_data* plv);
void plv_prepare(plv_data* plv);
void plv_render_string(char** buf, const char* str);

#endif