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|
{- Remote costs.
-
- Copyright 2011-2013 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Config.Cost where
{- We use a float for a cost to ensure that there is a cost in
- between any two other costs. -}
type Cost = Float
{- Some predefined default costs.
- Users setting costs in config files can be aware of these,
- and pick values relative to them. So don't change. -}
cheapRemoteCost :: Cost
cheapRemoteCost = 100
nearlyCheapRemoteCost :: Cost
nearlyCheapRemoteCost = 110
semiExpensiveRemoteCost :: Cost
semiExpensiveRemoteCost = 175
expensiveRemoteCost :: Cost
expensiveRemoteCost = 200
veryExpensiveRemoteCost :: Cost
veryExpensiveRemoteCost = 1000
{- Adjusts a remote's cost to reflect it being encrypted. -}
encryptedRemoteCostAdj :: Cost
encryptedRemoteCostAdj = 50
{- Given an ordered list of costs, and the position of one of the items
- the list, inserts a new cost into the list, in between the item
- and the item after it.
-
- If two or move items have the same cost, their costs are adjusted
- to make room. The costs of other items in the list are left
- unchanged.
-
- To insert the new cost before any other in the list, specify a negative
- position. To insert the new cost at the end of the list, specify a
- position longer than the list.
-}
insertCostAfter :: [Cost] -> Int -> [Cost]
insertCostAfter [] _ = []
insertCostAfter l pos
| pos < 0 = costBetween 0 (l !! 0) : l
| nextpos > maxpos = l ++ [1 + l !! maxpos]
| item == nextitem =
let (_dup:new:l') = insertCostAfter lastsegment 0
in firstsegment ++ [costBetween item new, new] ++ l'
| otherwise =
firstsegment ++ [costBetween item nextitem ] ++ lastsegment
where
nextpos = pos + 1
maxpos = length l - 1
item = l !! pos
nextitem = l !! nextpos
(firstsegment, lastsegment) = splitAt (pos + 1) l
costBetween :: Cost -> Cost -> Cost
costBetween x y
| x == y = x
| x > y = -- avoid fractions unless needed
let mid = y + (x - y) / 2
mid' = fromIntegral (floor mid :: Int)
in if mid' > y then mid' else mid
| otherwise = costBetween y x
{- Make sure the remote cost numbers work out. -}
prop_cost_sane :: Bool
prop_cost_sane = False `notElem`
[ expensiveRemoteCost > 0
, cheapRemoteCost < nearlyCheapRemoteCost
, nearlyCheapRemoteCost < semiExpensiveRemoteCost
, semiExpensiveRemoteCost < expensiveRemoteCost
, cheapRemoteCost + encryptedRemoteCostAdj > nearlyCheapRemoteCost
, nearlyCheapRemoteCost + encryptedRemoteCostAdj < semiExpensiveRemoteCost
, nearlyCheapRemoteCost + encryptedRemoteCostAdj < expensiveRemoteCost
]
|
