improvement data structure

Improvement data is in json format, it is parsed as an array, each element is an item with its improvement options and requirements, take 93-type sonar as example:

  {
    "id": 46,  // item id
    "type": "ソナー",   // item type, parsed in japanese
    "icon": 18,  // item icon, api_type[3]
    "name": "九三式水中聴音機",  // item name, parsed in japanese
    "improvement": [  // improvement options, an Array
      {
        "upgrade": {  // upgrade information, if not set, will be false
          "level": 3,  //  improvement level after upgrade
          "name": "三式水中探信儀",
          "icon": 18
        },
        "req": [  // short for requirement, an Array 
          {
            "day": [  // available days, beginning is Sunday
              true,
              false,
              false,
              false,
              false,
              true,
              true
            ],
            "secretary": [  // 2nd slot kanmusu
              "夕張"
            ]
          },
          {
            "day": [
              false,
              true,
              false,
              false,
              false,
              false,
              false
            ],
            "secretary": [
              "五十鈴改二"
            ]
          }
        ],
        "consume": {  // cost for improvement, material may vary from different stages 
          "fuel": 10,
          "ammo": 0,
          "steel": 30,
          "bauxite": 30,
          "material": [
            {
              "development": [ // development item
                2,  // essential
                2   // assured improvement
              ],
              "improvement": [  // development item, screw
                1, // essential
                2  // assured improvement
              ],
              "item": {  // item to consume
                "icon": 0,
                "name": "",
                "count": 0
              }
            },
            {
              "development": [
                3,
                4
              ],
              "improvement": [
                2,
                3
              ],
              "item": {
                "icon": 18,
                "name": "九三式水中聴音機",
                "count": 1
              }
            },
            {
              "development": [
                6,
                9
              ],
              "improvement": [
                3,
                5
              ],
              "item": {
                "icon": 18,
                "name": "九三式水中聴音機",
                "count": 2
              }
            }
          ]
        }
      },
     {
        "upgrade": {
          "level": 0,
          "name": "四式水中聴音機",
          "icon": 18
        },
        "req": [
          {
            "day": [
              false,
              false,
              false,
              false,
              true,
              true,
              false
            ],
            "secretary": [
              "五十鈴改二"
            ]
          },
          {
            "day": [
              true,
              false,
              false,
              false,
              true,
              true,
              true
            ],
            "secretary": [
              "時雨改二"
            ]
          },
          {
            "day": [
              true,
              false,
              false,
              false,
              false,
              true,
              true
            ],
            "secretary": [
              "香取改"
            ]
          }
        ],
        "consume": {
          "fuel": 10,
          "ammo": 0,
          "steel": 30,
          "bauxite": 30,
          "material": [
            {
              "development": [
                2,
                2
              ],
              "improvement": [
                1,
                2
              ],
              "item": {
                "icon": 0,
                "name": "",
                "count": 0
              }
            },
            {
              "development": [
                3,
                4
              ],
              "improvement": [
                2,
                3
              ],
              "item": {
                "icon": 18,
                "name": "九三式水中聴音機",
                "count": 1
              }
            },
            {
              "development": [
                10,
                20
              ],
              "improvement": [
                6,
                12
              ],
              "item": {
                "icon": 18,
                "name": "三式水中探信儀",
                "count": 2
              }
            }
          ]
        }
      }
    ]
  },