item price data, confidence and safety concerns

[Xeverous]

Few things are absolutely sure:

• Some unique items share their base with other uniques. This makes a lot of drops ambiguous ("Leather Belt") and makes filtering jewels and amulets pretty much impossible. We can not really fix this issue unless GGG implements something to disambiguate. It is a responsibility of filter's creator that ambiguous drops are labeled in special way to indicate the player has to verify them manually.
• Many items can have unreliable prices or no price information at all. Both poe.ninja and poe.watch report this by "low confidence" or simply by not providing price data for such item. It is a responsibility of filter's creator to ensure existence of no-price-query generic blocks and not writing entire filter only on the data supplied by market info.

However, there are some things we can work on:

• 1) We can fight price fixing by storing previous item prices, checking whether there is a significant difference. I'm not sure whether this should be done, because:
  • Economy overview sites (poe.ninja, poe.watch) generally do not store/report past item price information which makes it hard to detect that a specific item price has changed dramatically. And I do not want Filter Spirit to implement its own item price database.
  • Some items will change their value dramatically, eg by "the Mathil effect" or some balance patch
  • A lot of items (especially certain prophecies) have very unstable prices at the league start and it's completely normal
• 2) Both sites report prices both in exalted and in chaos. Which should be used inside filters? Implement and allow both?
• 3) How to deal with ambiguous names? Given code like $uniques | price(10, 1000) - should it output Sadist Garb when Inpulsa is expensive but Tinkerskin is 1c? Should we add another filter like | ambiguous(true)? We need a feature to let users decide what to do when multiple uniques share the same base type and some get in price range while others do not.

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My current plans are:

• 1) Sites already report confidence which should be enough. Just implement an option to treat all low-confidence price items as unknown value
• 2) Go with chaos. In case of exalted, majority of items would have a price in range 0.01 - 0.5 which makes it hard to work with. Values 1 - 100 feels much better. We can always add ex-based price querying later.
• 3) ???

[Xeverous]

First 2 points are already mentioned in the tutorial.

other points:

• 1) FS by default will ignore low confidence items
• 2) As above. Will implement ex pricing if requested.
• 3) The "bad drop"/"good drop"/"potentially good drop" is a common strategy in all major filters. FS allows the same by providing unambiguous and ambiguous unique item base types.