{-|
Module      : Toml.Position
Description : File position representation
Copyright   : (c) Eric Mertens, 2023
License     : ISC
Maintainer  : emertens@gmail.com

This module provides the 'Position' type for tracking locations
in files while doing lexing and parsing for providing more useful
error messages.

This module assumes 8 column wide tab stops.

-}
module Toml.Position (
    Position(..),
    startPos,
    move,
    ) where

-- | A position in a text file
data Position = Position {
    Position -> Int
posIndex  :: {-# UNPACK #-} !Int, -- ^ code-point index (zero-based)
    Position -> Int
posLine   :: {-# UNPACK #-} !Int, -- ^ line index (one-based)
    Position -> Int
posColumn :: {-# UNPACK #-} !Int  -- ^ column index (one-based)
    } deriving (
        ReadPrec [Position]
ReadPrec Position
Int -> ReadS Position
ReadS [Position]
(Int -> ReadS Position)
-> ReadS [Position]
-> ReadPrec Position
-> ReadPrec [Position]
-> Read Position
forall a.
(Int -> ReadS a)
-> ReadS [a] -> ReadPrec a -> ReadPrec [a] -> Read a
$creadsPrec :: Int -> ReadS Position
readsPrec :: Int -> ReadS Position
$creadList :: ReadS [Position]
readList :: ReadS [Position]
$creadPrec :: ReadPrec Position
readPrec :: ReadPrec Position
$creadListPrec :: ReadPrec [Position]
readListPrec :: ReadPrec [Position]
Read    {- ^ Default instance -},
        Int -> Position -> ShowS
[Position] -> ShowS
Position -> String
(Int -> Position -> ShowS)
-> (Position -> String) -> ([Position] -> ShowS) -> Show Position
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: Int -> Position -> ShowS
showsPrec :: Int -> Position -> ShowS
$cshow :: Position -> String
show :: Position -> String
$cshowList :: [Position] -> ShowS
showList :: [Position] -> ShowS
Show    {- ^ Default instance -},
        Eq Position
Eq Position =>
(Position -> Position -> Ordering)
-> (Position -> Position -> Bool)
-> (Position -> Position -> Bool)
-> (Position -> Position -> Bool)
-> (Position -> Position -> Bool)
-> (Position -> Position -> Position)
-> (Position -> Position -> Position)
-> Ord Position
Position -> Position -> Bool
Position -> Position -> Ordering
Position -> Position -> Position
forall a.
Eq a =>
(a -> a -> Ordering)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> Bool)
-> (a -> a -> a)
-> (a -> a -> a)
-> Ord a
$ccompare :: Position -> Position -> Ordering
compare :: Position -> Position -> Ordering
$c< :: Position -> Position -> Bool
< :: Position -> Position -> Bool
$c<= :: Position -> Position -> Bool
<= :: Position -> Position -> Bool
$c> :: Position -> Position -> Bool
> :: Position -> Position -> Bool
$c>= :: Position -> Position -> Bool
>= :: Position -> Position -> Bool
$cmax :: Position -> Position -> Position
max :: Position -> Position -> Position
$cmin :: Position -> Position -> Position
min :: Position -> Position -> Position
Ord     {- ^ Default instance -},
        Position -> Position -> Bool
(Position -> Position -> Bool)
-> (Position -> Position -> Bool) -> Eq Position
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: Position -> Position -> Bool
== :: Position -> Position -> Bool
$c/= :: Position -> Position -> Bool
/= :: Position -> Position -> Bool
Eq      {- ^ Default instance -})

-- | The initial 'Position' for the start of a file
startPos :: Position
startPos :: Position
startPos = Position { posIndex :: Int
posIndex = Int
0, posLine :: Int
posLine = Int
1, posColumn :: Int
posColumn = Int
1 }

-- | Adjust a file position given a single character handling
-- newlines and tabs. All other characters are considered to fill
-- exactly one column.
move :: Char -> Position -> Position
move :: Char -> Position -> Position
move Char
x Position{ posIndex :: Position -> Int
posIndex = Int
i, posLine :: Position -> Int
posLine = Int
l, posColumn :: Position -> Int
posColumn = Int
c} =
    case Char
x of
        Char
'\n' -> Position{ posIndex :: Int
posIndex = Int
iInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1, posLine :: Int
posLine = Int
lInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1, posColumn :: Int
posColumn = Int
1 }
        Char
'\t' -> Position{ posIndex :: Int
posIndex = Int
iInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1, posLine :: Int
posLine = Int
l, posColumn :: Int
posColumn = (Int
c Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
7) Int -> Int -> Int
forall a. Integral a => a -> a -> a
`quot` Int
8 Int -> Int -> Int
forall a. Num a => a -> a -> a
* Int
8 Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
1 }
        Char
_    -> Position{ posIndex :: Int
posIndex = Int
iInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1, posLine :: Int
posLine = Int
l, posColumn :: Int
posColumn = Int
cInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1 }