npctrade: revisit price rules

[andrei8l]

Summary

None

Purpose of change

Update shopkeeper price rules with new EOC technology

Describe the solution

Allow selecting items by item conditions

Example:This blacklist blocks cannibal food

  {
    "id": "no_cannibals",
    "type": "shopkeeper_blacklist",
    "entries": [ { "item_condition": { "math": [ "n_vitamin('human_flesh_vitamin') > 0" ] }, "message": "!!!CANNIBAL!!!" } ]
  },

Example:This price rule increases markup for heavy items

    "price_rules": [
      { "item_condition": { "math": [ " n_weight() >= 10000000 " ] }, "markup": 2 }
    ],

Allow price adjustments to use dialogue variables/math functions

Example: The price for strawberries varies with day of year, bottoming out in the middle of summer and topping in the middle of winter

  {
    "type": "jmath_function",
    "id": "year_length",
    "num_args": 0,
    "return": "game_option('SEASON_LENGTH') * 4"
  },
  {
    "type": "jmath_function",
    "id": "day_of_year",
    "num_args": 0,
    "return": "time('now', 'unit': 'days') % year_length()"
  },
  {
    "type": "faction",
    "id": "strawberry_merchants",
    "name": "The Straberry Merchants",
    "likes_u": 30,
    "respects_u": 30,
    "known_by_u": false,
    "size": 100,
    "power": 100,
    "fac_food_supply": { "calories": 9000000000, "vitamins": { "iron": 288000, "calcium": 288000, "vitC": 288000 } },
    "wealth": 75000000,
    "currency": "FMCNote",
    "price_rules": [
      {
        "item": "strawberries",
        "premium": { "math": [ "1 + 0.5 * sin((day_of_year() + 3*year_length()/8) * 2*pi/year_length())" ] }
      }
    ],

This was my original reason for writing math

Describe alternatives you've considered

N/A

Testing

Updated test units

Additional context

N/A