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## This module implements a simple TNetstring parser and serializer.

## TNetString stands for "tagged netstring" and is a modification of Dan

## Bernstein's netstrings specification.  TNetstrings allow for the same data

## structures as JSON but in a format that is resistant to buffer overflows

## and backward compatible with original netstrings.  They make no assumptions

## about string contents, allowing for easy transmission of binary data mixed

## with strongly typed values.

## See http://cr.yp.to/proto/netstrings.txt and http://tnetstrings.org/ for additional information.

##

## This module borrows heavily (in both usage and code) from the nim JSON stdlib

## (json.nim) -- (c) Copyright 2015 Andreas Rumpf, Dominik Picheta.

## 

## Usage example:

##

## .. code-block:: nim

##

##   let

##       tnetstr = "52:4:test,3:1.3^4:key2,4:true!6:things,12:1:1#1:2#1:3#]}"

##       tnetobj = parse_tnetstring( tnetstr )

##

##   # tnetobj is now equivalent to the structure:

##   # @[(key: test, val: 1.3), (key: key2, val: true), (key: things, val: @[1, 2, 3])]

##

##   assert( tnetobj.kind == TNetstringObject )

##   echo tnetobj[ "test" ]

##   echo tnetobj[ "key2" ]

##   for item in tnetobj[ "things" ]:

##       echo item

##   

## Results in:

##

## .. code-block:: nim

##

##   1.3

##   true

##   1

##   2

##   3

##

## This module can also be used to reasonably create a serialized

## TNetstring, suitable for network transmission:

##

## .. code-block:: nim

##    

##    let

##        number  = 1000

##        list    = @[ "thing1", "thing2" ]

##        tnettop = newTNetstringArray() # top-level array

##        tnetsub = newTNetstringArray() # sub array

##    

##    tnettop.add( newTNetstringInt(number) )

##    for item in list:

##        tnetsub.add( newTNetstringString(item) )

##    tnettop.add( tnetsub )

##    

##    # Equivalent to: @[1000, @[thing1, thing2]]

##    echo dump_tnetstring( tnettop )

##

## Results in:

##

## .. code-block:: nim

##    

##    29:4:1000#18:6:thing1,6:thing2,]]

##

import

    hashes,

    parseutils,

    strutils

type 

  TNetstringKind* = enum     ## enumeration of all valid types

    TNetstringString,        ## a string literal

    TNetstringInt,           ## an integer literal

    TNetstringFloat,         ## a float literal

    TNetstringBool,          ## a ``true`` or ``false`` value

    TNetstringNull,          ## the value ``null``

    TNetstringObject,        ## an object: the ``}`` token

    TNetstringArray          ## an array: the ``]`` token

  TNetstringNode* = ref TNetstringNodeObj

  TNetstringNodeObj* {.acyclic.} = object

      extra*: string

      case kind*: TNetstringKind

      of TNetstringString:

          str*: string

      of TNetstringInt:

          num*: BiggestInt

      of TNetstringFloat:

          fnum*: float

      of TNetstringBool:

          bval*: bool

      of TNetstringNull:

          nil

      of TNetstringObject:

          fields*: seq[ tuple[key: string, val: TNetstringNode] ]

      of TNetstringArray:

          elems*: seq[ TNetstringNode ]

  TNetstringParseError* = object of ValueError ## Raised for a TNetstring error

proc raiseParseErr*( t: TNetstringNode, msg: string ) {.noinline, noreturn.} =

  ## Raises a `TNetstringParseError` exception.

  raise newException( TNetstringParseError, msg )

proc newTNetstringString*( s: string ): TNetstringNode =

    ## Create a new String typed TNetstringNode.

proc newTNetstringInt*( i: BiggestInt ): TNetstringNode =

    ## Create a new Integer typed TNetstringNode.

proc newTNetstringFloat*( f: float ): TNetstringNode =

    ## Create a new Float typed TNetstringNode.

proc newTNetstringBool*( b: bool ): TNetstringNode =

    ## Create a new Boolean typed TNetstringNode.

proc newTNetstringNull*(): TNetstringNode =

    ## Create a new nil typed TNetstringNode.

proc newTNetstringObject*(): TNetstringNode =

    ## Create a new Object typed TNetstringNode.

proc newTNetstringArray*(): TNetstringNode =

    ## Create a new Array typed TNetstringNode.

proc getStr*( node: TNetstringNode, default: string = "" ): string =

    ## Retrieves the string value of a `TNetstringString TNetstringNodee`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringString``.

    if node.kind != TNetstringString: return default

    return node.str

proc getInt*( node: TNetstringNode, default: BiggestInt = 0 ): BiggestInt =

    ## Retrieves the int value of a `TNetstringInt TNetstringNode`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringInt``.

    if node.kind != TNetstringInt: return default

    return node.num

proc getFloat*( node: TNetstringNode, default: float = 0.0 ): float =

    ## Retrieves the float value of a `TNetstringFloat TNetstringNode`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringFloat``.

    if node.kind != TNetstringFloat: return default

    return node.fnum

proc getBool*( node: TNetstringNode, default: bool = false ): bool =

    ## Retrieves the bool value of a `TNetstringBool TNetstringNode`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringBool``.

    if node.kind != TNetstringBool: return default

    return node.bval

proc getFields*( node: TNetstringNode,

    default: seq[tuple[key: string, val: TNetstringNode]] = @[] ):

        seq[tuple[key: string, val: TNetstringNode]] =

    ## Retrieves the key, value pairs of a `TNetstringObject TNetstringNode`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringObject``.

    if node.kind != TNetstringObject: return default

    return node.fields

proc getElems*( node: TNetstringNode, default: seq[TNetstringNode] = @[] ): seq[TNetstringNode] =

    ## Retrieves the values of a `TNetstringArray TNetstringNode`.

    ## Returns ``default`` if ``node`` is not a ``TNetstringArray``.

    if node.kind != TNetstringArray: return default

    return node.elems

proc parse_tnetstring*( data: string ): TNetstringNode =

    ## Given an encoded tnetstring, parse and return a TNetstringNode.

    var

        length:  int

        kind:    char

        payload: string

        extra:   string

    let sep_pos = data.skipUntil( ':' )

    if sep_pos == data.len: raiseParseErr( result, "Invalid data: No separator token found." )

    try:

        length       = data[ 0 .. sep_pos - 1 ].parseInt

        kind         = data[ sep_pos + length + 1 ]

        payload      = data[ sep_pos + 1 .. sep_pos + length ]

        extra        = data[ sep_pos + length + 2 .. ^1 ]

        var msg = getCurrentExceptionMsg()

        raiseParseErr( result, msg )

    case kind:

        of ',':

            result = newTNetstringString( payload )

        of '#':

            try:

                result = newTNetstringInt( payload.parseBiggestInt )

            except ValueError:

                var msg = getCurrentExceptionMsg()

                raiseParseErr( result, msg )

        of '^':

            try:

                result = newTNetstringFloat( payload.parseFloat )

            except ValueError:

                var msg = getCurrentExceptionMsg()

                raiseParseErr( result, msg )

        of '!':

            result = newTNetstringBool( payload == "true" )

        of '~':

            if length != 0: raiseParseErr( result, "Invalid data: Payload must be 0 length for null." )

            result = newTNetstringNull()

        of ']':

            result = newTNetstringArray()

            var subnode = parse_tnetstring( payload )

            result.elems.add( subnode )

            while subnode.extra != "":

                subnode = parse_tnetstring( subnode.extra )

                result.elems.add( subnode )

        of '}':

            result = newTNetstringObject()

            var key = parse_tnetstring( payload )

            if ( key.extra == "" ): raiseParseErr( result, "Invalid data: Unbalanced tuple." )

            if ( key.kind != TNetstringString ): raiseParseErr( result, "Invalid data: Object keys must be strings." )

            var value = parse_tnetstring( key.extra )

            result.fields.add( (key: key.str, val: value) )

            while value.extra != "":

                var subkey = parse_tnetstring( value.extra )

                if ( subkey.extra == "" ): raiseParseErr( result, "Invalid data: Unbalanced tuple." )

                if ( subkey.kind != TNetstringString ): raiseParseErr( result, "Invalid data: Object keys must be strings." )

                value = parse_tnetstring( subkey.extra )

                result.fields.add( (key: subkey.str, val: value) )

        else:

            raiseParseErr( result, "Invalid data: Unknown tnetstring type '$1'." % $kind )

    result.extra = extra

iterator items*( node: TNetstringNode ): TNetstringNode =

    ## Iterator for the items of `node`. `node` has to be a TNetstringArray.

    assert node.kind == TNetstringArray

    for i in items( node.elems ):

        yield i

iterator mitems*( node: var TNetstringNode ): var TNetstringNode =

    ## Iterator for the items of `node`. `node` has to be a TNetstringArray. Items can be

    ## modified.

    assert node.kind == TNetstringArray

    for i in mitems( node.elems ):

        yield i

iterator pairs*( node: TNetstringNode ): tuple[ key: string, val: TNetstringNode ] =

    ## Iterator for the child elements of `node`. `node` has to be a TNetstringObject.

    assert node.kind == TNetstringObject

    for key, val in items( node.fields ):

        yield ( key, val )

iterator mpairs*( node: var TNetstringNode ): var tuple[ key: string, val: TNetstringNode ] =

    ## Iterator for the child elements of `node`. `node` has to be a TNetstringObject.

    ## Items can be modified.

    assert node.kind == TNetstringObject

    for keyVal in mitems( node.fields ):

        yield keyVal

proc `$`*( node: TNetstringNode ): string =

    ## Delegate stringification of `TNetstringNode` to its underlying object.

    return case node.kind:

    of TNetstringString:

        $node.str

    of TNetstringInt:

        $node.num

    of TNetstringFloat:

        $node.fnum

    of TNetstringBool:

        $node.bval

    of TNetstringNull:

        "(nil)"

    of TNetstringArray:

        $node.elems

    of TNetstringObject:

        $node.fields

proc `==`* ( a, b: TNetstringNode ): bool =

    ## Check two TNetstring nodes for equality.

    if a.isNil:

        if b.isNil: return true

        return false

    elif b.isNil or a.kind != b.kind:

        return false

    else:

        return case a.kind

        of TNetstringString:

            a.str == b.str

        of TNetstringInt:

            a.num == b.num

        of TNetstringFloat:

            a.fnum == b.fnum

        of TNetstringBool:

            a.bval == b.bval

        of TNetstringNull:

            true

        of TNetstringArray:

            a.elems == b.elems

        of TNetstringObject:

            a.fields == b.fields

proc copy*( node: TNetstringNode ): TNetstringNode =

    ## Perform a deep copy of TNetstringNode.

    case node.kind

    of TNetstringString:

        result.str = node.str

    of TNetstringInt:

        result.num = node.num

    of TNetstringFloat:

        result.fnum = node.fnum

    of TNetstringBool:

        result.bval = node.bval

    of TNetstringNull:

        discard

    of TNetstringArray:

        result.elems = @[]

        for item in items( node ):

            result.elems.add( copy(item) )

    of TNetstringObject:

        result.fields = @[]

        for key, value in items( node.fields ):

            result.fields.add( (key, copy(value)) )

proc delete*( node: TNetstringNode, key: string ) =

    ## Deletes ``node[key]`` preserving the order of the other (key, value)-pairs.

    assert( node.kind == TNetstringObject )

    for i in 0..node.fields.len - 1:

        if node.fields[i].key == key:

            node.fields.delete( i )

            return

proc hash*( node: TNetstringNode ): Hash =

    ## Compute the hash for a TNetstringString node

    return case node.kind

    of TNetstringString:

        hash( node.str )

    of TNetstringInt:

        hash( node.num )

    of TNetstringFloat:

        hash( node.fnum )

    of TNetstringBool:

        hash( node.bval.int )

    of TNetstringNull:

        hash( 0 )

    of TNetstringArray:

        hash( node.elems )

    of TNetstringObject:

        hash( node.fields )

proc len*( node: TNetstringNode ): int =

    ## If `node` is a `TNetstringArray`, it returns the number of elements.

    ## If `node` is a `TNetstringObject`, it returns the number of pairs.

    ## If `node` is a `TNetstringString`, it returns strlen.

    ## Else it returns 0.

    return case node.kind

    of TNetstringString:

        node.str.len

    of TNetstringArray:

        node.elems.len

    of TNetstringObject:

        node.fields.len

    else:

        0

proc `[]`*( node: TNetstringNode, name: string ): TNetstringNode =

    ## Gets a field from a `TNetstringNode`, which must not be nil.

    ## If the value at `name` does not exist, returns nil

    assert( not isNil(node) )

    assert( node.kind == TNetstringObject )

    for key, item in node:

        if key == name:

            return item

    return nil

proc `[]`*( node: TNetstringNode, index: int ): TNetstringNode =

    ## Gets the node at `index` in an Array. Result is undefined if `index`

    ## is out of bounds.

    assert( not isNil(node) )

    assert( node.kind == TNetstringArray )

    return node.elems[ index ]

proc hasKey*( node: TNetstringNode, key: string ): bool =

    ## Checks if `key` exists in `node`.

    assert( node.kind == TNetstringObject )

    for k, item in items( node.fields ):

        if k == key: return true

proc add*( parent, child: TNetstringNode ) =

    ## Appends `child` to a TNetstringArray node `parent`.

    assert( parent.kind == TNetstringArray )

    parent.elems.add( child )

proc add*( node: TNetstringNode, key: string, val: TNetstringNode ) =

    ## Adds ``(key, val)`` pair to the TNetstringObject `node`.

    ## For speed reasons no check for duplicate keys is performed.

    ## (Note, ``[]=`` performs the check.)

    assert( node.kind == TNetstringObject )

    node.fields.add( (key, val) )

proc `[]=`*( node: TNetstringNode, index: int, val: TNetstringNode ) =

    ## Sets an index for a `TNetstringArray`.

    assert( node.kind == TNetstringArray )

    node.elems[ index ] = val

proc `[]=`*( node: TNetstringNode, key: string, val: TNetstringNode ) =

    ## Sets a field from a `TNetstringObject`. Performs a check for duplicate keys.

    assert( node.kind == TNetstringObject )

    for i in 0 .. node.fields.len - 1:

        if node.fields[i].key == key:

            node.fields[i].val = val

            return

    node.fields.add( (key, val) )

proc dump_tnetstring*( node: TNetstringNode ): string =

    ## Renders a TNetstring `node` as a regular string.

    case node.kind

    of TNetstringString:

        result = $( node.str.len ) & ':' & node.str & ','

    of TNetstringInt:

        let str = $( node.num )

        result = $( str.len ) & ':' & str & '#'

    of TNetstringFloat:

        let str = $( node.fnum )

        result = $( str.len ) & ':' & str & '^'

    of TNetstringBool:

        result = if node.bval: "4:true!" else: "5:false!"

    of TNetstringNull:

        result = "0:~"

    of TNetstringArray:

        result = ""

        for n in node.items:

            result = result & n.dump_tnetstring

        result = $( result.len ) & ':' & result & ']'

    of TNetstringObject:

        result = ""

        for key, val in node.pairs:

            result = result & $( key.len ) & ':' & key & ',' # key

            result = result & val.dump_tnetstring            # val

        result = $( result.len ) & ':' & result & '}'