[nit.git] / lib / standard / ropes.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# This file is free software, which comes along with NIT.  This software is
# distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A
# PARTICULAR PURPOSE.  You can modify it if you want,  provided this header
# is kept unaltered, and a notification of the changes is added.
# You  are  allowed  to  redistribute it and sell it, alone or as a part of
# another product.

# Nit implementation of the Ropes (see Ropes : An Alternative to Strings,
# SOFTWARE - PRACTICE AND EXPERIENCE, VOL. 25(12), 1315 - 1330 (DECEMBER 1995)
# Hans. J Boehm, Russ Atkinson and Michael Plass)
#
# A rope is a kind of string but instead of being flat, it relies on a binary tree structure to store data.
module ropes

intrude import string

# Used when searching for a particular node
# Returns the path to the node from the root of the rope
# Also, the node and the offset for seeked position in the rope
private class Path
        # Leaf found
        var leaf: Leaf
        # Offset in leaf
        var offset: Int
        # Stack of the nodes traversed, and the path used
        var stack: List[PathElement]
end

# An element for a Path, has the concat node and whether or not
# left or right child was visited.
private class PathElement
        # Visited node
        var node: Concat
        # Was the left child visited ?
        var left = false
        # Was the right child visited ?
        var right = false
end

# A node for a Rope
private abstract class RopeNode
        # Length of the node
        var length = 0

        # Transforms the current node to a Leaf.
        # This might be costly to invoke since this produces a FlatString concatenation.
        # Can be used internally to limit the growth of the Rope when working with small leaves.
        fun to_leaf: Leaf is abstract
end

# Node that represents a concatenation between two nodes (of any RopeNode type)
private class Concat
        super RopeNode

        # Left child of the node
        var left: nullable RopeNode
        # Right child of the node
        var right: nullable RopeNode

        init(l: nullable RopeNode, r: nullable RopeNode)
        do
                left = l
                right = r
                if l != null then length += l.length
                if r != null then length += r.length
        end

        redef fun to_leaf
        do
                if left == null then
                        if right == null then return new StringLeaf("".as(FlatString))
                        return right.to_leaf
                end
                if right == null then return left.as(not null).to_leaf
                return new StringLeaf((left.to_leaf.str.as(FlatString) + right.to_leaf.str.as(FlatString)).as(FlatString))
        end
end

# Leaf of a Rope, contains a FlatString
private abstract class Leaf
        super RopeNode

        # Encapsulated FlatString in the leaf node
        var str: FlatText

end

private class StringLeaf
        super Leaf

        init(val: FlatString) do
                self.str = val
                length = str.length
        end

        redef fun to_leaf do return self
end

# Used as a cache when using indexed access to a substring in the Rope
private class LeafCache
        # Cached leaf
        var leaf: Leaf
        # Position in Rope
        var pos: Int
end

# Basic structure, binary tree with a root node.
#
# Also shared services by subsequent implementations.
abstract class Rope
        super Text

        # Root node, entry point of a Rope.
        private var root: RopeNode

        # Cached version of self as a flat String
        private var str_representation: nullable NativeString = null

        private var leaf_cache: nullable LeafCache = null

        # Empty Rope
        init do from("")

        # Creates a new Rope with `s` as root
        init from(s: String) do
                if s isa RopeString then root = s.root else root = new StringLeaf(s.as(FlatString))
        end

        private init from_root(r: RopeNode)
        do
                root = r
        end

        redef fun length do return root.length

        # Iterator on the nodes of the rope, in forward postfix order
        private fun postfix(from: Int): Postfix do return new Postfix.from(self, from)

        # Iterator on the leaves of the rope, forward order
        private fun leaves(from: Int): LeavesIterator do return new LeavesIterator(self, from)

        # Iterator on the substrings from 0, in forward order
        redef fun substrings do return new SubstringsIterator(self, 0)

        # Iterator on the substrings, starting at position `from`, in forward order
        fun substrings_from(from: Int): IndexedIterator[Text] do return new SubstringsIterator(self, from)

        # Iterator on the nodes of the rope, in backwards postfix order
        private fun reverse_postfix(from: Int): ReversePostfix do return new ReversePostfix.from(self, from)

        # Iterator on the leaves of the rope, backwards order
        private fun reverse_leaves(from: Int): ReverseLeavesIterator do return new ReverseLeavesIterator(self,from)

        # Iterator on the substrings, in reverse order
        fun reverse_substrings: IndexedIterator[Text] do return new ReverseSubstringsIterator(self, length-1)

        # Iterator on the substrings, in reverse order, starting iteration at position `from`
        fun reverse_substrings_from(from: Int): IndexedIterator[Text] do return new ReverseSubstringsIterator(self, from)

        redef fun output
        do
                for i in substrings do
                        i.output
                end
        end

        redef fun to_cstring
        do
                if str_representation != null then return str_representation.as(not null)

                var native_final_str = calloc_string(length + 1)

                native_final_str[length] = '\0'

                if self.length == 0 then
                        str_representation = native_final_str
                        return native_final_str
                end

                var offset = 0

                for i in substrings do
                        var str = i.flatten
                        if str isa FlatString then str.items.copy_to(native_final_str, str.length, str.index_from, offset)
                        offset += i.length
                end

                str_representation = native_final_str

                return native_final_str
        end

        # Path to the Leaf for `position`
        private fun node_at(position: Int): Path
        do
                assert position >= 0 and position <= length
                if position == length then
                        var st = new List[PathElement]
                        stack_to_end(root,st)
                        if not st.is_empty then
                                var lst = st.last
                                var lf = lst.node.right
                                if lf != null then
                                        return new Path(lf.as(Leaf), lf.length, st)
                                else
                                        lf = lst.node.left
                                        return new Path(lf.as(Leaf), lf.length, st)
                                end
                        else
                                return new Path(root.as(Leaf), length, st)
                        end
                end
                return get_node_from(root, 0, position, new List[PathElement])
        end

        # Special case for when the required pos is length
        private fun stack_to_end(nod: RopeNode, st: List[PathElement])
        do
                if nod isa Leaf then return
                var n = nod.as(Concat)
                var r = n.right
                var ele = new PathElement(n)
                ele.right = true
                st.push(ele)
                if r != null then
                        stack_to_end(r, st)
                end
                return
        end

        # Builds the path to Leaf at position `seek_pos`
        private fun get_node_from(node: RopeNode, curr_pos: Int, seek_pos: Int, stack: List[PathElement]): Path
        do
                assert curr_pos >= 0
                if node isa Leaf then
                        self.leaf_cache = new LeafCache(node, curr_pos)
                        return new Path(node, seek_pos - curr_pos, stack)
                end
                node = node.as(Concat)

                if node.left != null then
                        var next_pos = curr_pos + node.left.length
                        stack.add(new PathElement(node))
                        if next_pos > seek_pos then
                                stack.last.left = true
                                return get_node_from(node.left.as(not null), curr_pos, seek_pos, stack)
                        end
                        stack.last.right = true
                        return get_node_from(node.right.as(not null), next_pos, seek_pos, stack)
                else
                        var vis = new PathElement(node)
                        vis.right = true
                        stack.add(vis)
                        return get_node_from(node.right.as(not null), curr_pos, seek_pos, stack)
                end
        end

        redef fun ==(o)
        do
                if not o isa Text then return false
                if o.length != self.length then return false
                var oit = o.chars.iterator
                for i in self.chars.iterator do
                        if i != oit.item then return false
                        oit.next
                end
                return true
        end
end

# Rope that cannot be modified
class RopeString
        super Rope
        super String

        redef fun to_s do return self

        redef fun empty do return once new RopeString.from("")

        redef var chars: SequenceRead[Char] = new RopeStringChars(self)

        redef fun reversed
        do
                var ret = empty
                for i in substrings do
                        ret = i.as(String).reversed + ret
                end
                return ret
        end

        redef fun to_upper
        do
                var ret = empty
                for i in substrings do
                        ret += i.as(String).to_upper
                end
                return ret
        end

        redef fun to_lower
        do
                var ret = empty
                for i in substrings do
                        ret += i.as(String).to_lower
                end
                return ret
        end

        redef fun +(o) do
                if self.length == 0 then return o.to_s
                if o.length == 0 then return self
                var str = o.to_s
                if str isa FlatString then
                        return new RopeString.from_root(new Concat(root, new StringLeaf(str)))
                else if str isa RopeString then
                        return new RopeString.from_root(new Concat(root, str.root))
                else
                        abort
                end
        end

        redef fun *(n)
        do
                var ret = new RopeString.from("")
                for i in [0..n[ do
                        ret = (ret + self).as(RopeString)
                end
                return ret
        end

        # Inserts a String `str` at position `pos`
        redef fun insert_at(str, pos)
        do
                if str.length == 0 then return self
                if self.length == 0 then return new RopeString.from(str)

                assert pos >= 0 and pos <= length

                var path = node_at(pos)

                var last_concat: Concat

                if path.offset == 0 then
                        if str isa FlatString then
                                last_concat = new Concat(new StringLeaf(str), path.leaf)
                        else
                                last_concat = new Concat(str.as(RopeString).root, path.leaf)
                        end
                else if path.offset == path.leaf.length then
                        if str isa FlatString then
                                last_concat = new Concat(path.leaf, new StringLeaf(str))
                        else
                                last_concat = new Concat(path.leaf, str.as(RopeString).root)
                        end
                else
                        var s = path.leaf.str
                        var l_half = s.substring(0, s.length - path.offset)
                        var r_half = s.substring_from(s.length - path.offset)
                        var cct: Concat
                        var ll = new StringLeaf(l_half.as(FlatString))
                        if str isa FlatString then
                                cct = new Concat(ll, new StringLeaf(str))
                        else
                                cct = new Concat(ll, str.as(RopeString).root)
                        end
                        last_concat = new Concat(cct, new StringLeaf(r_half.as(FlatString)))
                end

                for i in path.stack.reverse_iterator do
                        if i.left then
                                last_concat = new Concat(last_concat, i.node.right)
                        else
                                last_concat = new Concat(i.node.left, last_concat)
                        end
                end

                return new RopeString.from_root(last_concat)
        end

        # O(log(n))
        #
        #     var rope = new RopeString.from("abcd")
        #     assert rope.substring(1, 2)         ==  "bc"
        #     assert rope.substring(-1, 2)         ==  "a"
        #     assert rope.substring(1, 0)         ==  ""
        #     assert rope.substring(2, 5)         ==  "cd"
        #
        redef fun substring(pos, len)
        do
                if pos < 0 then
                        len += pos
                        pos = 0
                end

                if pos + len > length then len = length - pos

                if len <= 0 then return new RopeString.from("")

                var path = node_at(pos)

                var lf = path.leaf
                var offset = path.offset

                if path.leaf.str.length - offset > len then lf = new StringLeaf(lf.str.substring(offset,len).as(FlatString)) else lf = new StringLeaf(lf.str.substring_from(offset).as(FlatString))

                var nod: RopeNode = lf

                for i in path.stack.reverse_iterator do
                        if i.right then continue
                        nod = new Concat(nod, i.node.right)
                end

                var ret = new RopeString
                ret.root = nod

                path = ret.node_at(len-1)

                offset = path.offset
                nod = new StringLeaf(path.leaf.str.substring(0, offset+1).as(FlatString))

                for i in path.stack.reverse_iterator do
                        if i.left then continue
                        nod = new Concat(i.node.left, nod)
                end

                ret.root = nod

                return ret
        end
end

redef class FlatString

        redef fun insert_at(s, pos)
        do

                if pos == 0 then
                        var r = new RopeString.from(s)
                        return r + self
                end
                if pos == length then
                        var r = new RopeString.from(self)
                        return r + s
                end

                var l = substring(0,pos)
                var r = substring_from(pos)
                var ret: String = new RopeString.from(l)
                ret += s
                return ret + r
        end

end

private class RopeStringChars
        super SequenceRead[Char]

        var tgt: Rope

        redef fun [](pos)
        do
                assert pos < tgt.length
                if tgt.leaf_cache != null and pos >= tgt.leaf_cache.pos and (tgt.leaf_cache.pos + tgt.leaf_cache.leaf.length) > pos then return tgt.leaf_cache.leaf.str.chars[pos - tgt.leaf_cache.pos]
                var path = tgt.node_at(pos)
                return path.leaf.str.chars[path.offset]
        end

        redef fun iterator do return iterator_from(0)

        redef fun iterator_from(pos) do return new RopeCharIterator(tgt, pos)

        redef fun reverse_iterator do return reverse_iterator_from(tgt.length-1)

        redef fun reverse_iterator_from(pos) do return new ReverseRopeCharIterator(tgt, pos)
end

# Used to iterate on a Rope
private class IteratorElement

        init(e: RopeNode)
        do
                if e isa Leaf then
                        left = true
                        right = true
                end
                node = e
        end

        # The node being visited
        var node: RopeNode
        # If the node has a left child, was it visited ?
        var left = false
        # If the node has a right child, was it visited ?
        var right = false
        # Was the current node visited ?
        var done = false
end

# Simple Postfix iterator on the nodes of a Rope
private class Postfix
        super IndexedIterator[RopeNode]

        # Target Rope to iterate on
        var target: Rope

        # Current position in Rope
        var pos: Int

        # Visited nodes
        var stack = new List[IteratorElement]

        init from(tgt: Rope, pos: Int)
        do
                self.target = tgt
                self.pos = pos
                if pos < 0 or pos >= tgt.length then return
                var path = tgt.node_at(pos)
                self.pos -= path.offset
                for i in path.stack do
                        var item = new IteratorElement(i.node)
                        item.left = true
                        if i.right then item.right = true
                        stack.push item
                end
                var item = new IteratorElement(path.leaf)
                item.done = true
                stack.push item
        end

        redef fun item
        do
                assert is_ok
                return stack.last.node
        end

        redef fun is_ok do return not stack.is_empty

        redef fun index do return pos

        redef fun next do
                if stack.is_empty then return
                if pos > target.length-1 then
                        stack.clear
                        return
                end
                var lst = stack.last
                if lst.done then
                        if lst.node isa Leaf then
                                pos += lst.node.length
                        end
                        stack.pop
                        next
                        return
                end
                if not lst.left then
                        lst.left = true
                        var nod = lst.node
                        if nod isa Concat and nod.left != null then
                                stack.push(new IteratorElement(nod.left.as(not null)))
                                next
                                return
                        end
                end
                if not lst.right then
                        lst.right = true
                        var nod = lst.node
                        if nod isa Concat and nod.right != null then
                                stack.push(new IteratorElement(nod.right.as(not null)))
                                next
                                return
                        end
                end
                lst.done = true
        end
end

# Iterates on the leaves (substrings) of the Rope
class LeavesIterator
        super IndexedIterator[Leaf]

        private var nodes: Postfix

        init(tgt: Rope, pos: Int)
        do
                nodes = tgt.postfix(pos)
        end

        redef fun is_ok do return nodes.is_ok

        redef fun item
        do
                assert is_ok
                return nodes.item.as(Leaf)
        end

        redef fun index do return nodes.index

        redef fun next
        do
                while nodes.is_ok do
                        nodes.next
                        if nodes.is_ok and nodes.item isa Leaf then break
                end
        end
end

# Uses the leaves and calculates a new substring on each iteration
class SubstringsIterator
        super IndexedIterator[Text]

        private var nodes: IndexedIterator[Leaf]

        # Current position in Rope
        var pos: Int

        # Current substring, computed from the current Leaf and indexes
        var substring: Text

        init(tgt: Rope, pos: Int)
        do
                nodes = tgt.leaves(pos)
                self.pos = pos
                if pos < 0 or pos >= tgt.length then return
                make_substring
        end

        # Compute the bounds of the current substring and makes the substring
        private fun make_substring
        do
                substring = nodes.item.str
                var min = 0
                var length = substring.length
                if nodes.index < pos then
                        min = pos - nodes.index
                end
                substring = substring.substring(min, length)
        end

        redef fun is_ok do return nodes.is_ok

        redef fun item
        do
                assert is_ok
                return substring
        end

        redef fun index do return pos

        redef fun next
        do
                pos += substring.length
                nodes.next
                if nodes.is_ok then make_substring
        end

end

class RopeCharIterator
        super IndexedIterator[Char]

        var substrings: IndexedIterator[Text]

        var pos: Int

        var max: Int

        var substr_iter: IndexedIterator[Char]

        init(tgt: Rope, from: Int)
        do
                substrings = tgt.substrings_from(from)
                max = tgt.length - 1
                if not substrings.is_ok then
                        pos = tgt.length
                        return
                end
                pos = from
                substr_iter = substrings.item.chars.iterator
        end

        redef fun item do return substr_iter.item

        redef fun is_ok do return pos <= max

        redef fun index do return pos

        redef fun next
        do
                pos += 1
                if substr_iter.is_ok then
                        substr_iter.next
                end
                if not substr_iter.is_ok then
                        substrings.next
                        if substrings.is_ok then
                                substr_iter = substrings.item.chars.iterator
                        end
                end
        end
end

private class ReversePostfix
        super IndexedIterator[RopeNode]

        var target: Rope

        var pos: Int

        var min = 0

        var stack = new List[IteratorElement]

        init from(tgt: Rope, pos: Int)
        do
                self.pos = pos
                target = tgt
                if pos < 0 or pos >= tgt.length then return
                var path = tgt.node_at(pos)
                self.pos -= path.offset
                for i in path.stack do
                        var elemt = new IteratorElement(i.node)
                        elemt.right = true
                        if i.left then
                                elemt.left = true
                        end
                        stack.push elemt
                end
                stack.push(new IteratorElement(path.leaf))
                stack.last.done = true
        end

        redef fun item do
                assert is_ok
                return stack.last.node
        end

        redef fun is_ok do return not stack.is_empty

        redef fun index do return pos

        redef fun next
        do
                if stack.is_empty then return
                if pos < min then
                        stack.clear
                        return
                end
                var lst = stack.last
                if lst.done then
                        stack.pop
                        next
                        return
                end
                if not lst.right then
                        var nod = lst.node.as(Concat)
                        var rgt = nod.right
                        lst.right = true
                        if rgt != null then
                                stack.push(new IteratorElement(rgt))
                                next
                                return
                        end
                end
                if not lst.left then
                        var nod = lst.node.as(Concat)
                        var lft = nod.left
                        lst.left = true
                        if lft != null then
                                stack.push(new IteratorElement(lft))
                                next
                                return
                        end
                end
                if lst.node isa Leaf then pos -= lst.node.length
                lst.done = true
        end
end

private class ReverseLeavesIterator
        super IndexedIterator[Leaf]

        var nodes: ReversePostfix

        init(tgt: Rope, from: Int)
        do
                nodes = tgt.reverse_postfix(from)
        end

        redef fun is_ok do return nodes.is_ok

        redef fun item do
                assert is_ok
                return nodes.item.as(Leaf)
        end

        redef fun next do
                while nodes.is_ok do
                        nodes.next
                        if nodes.is_ok then if nodes.item isa Leaf then break
                end
        end

        redef fun index do return nodes.index

end

private class ReverseSubstringsIterator
        super IndexedIterator[Text]

        var leaves: ReverseLeavesIterator

        var pos: Int

        var str: Text

        init(tgt: Rope, from: Int)
        do
                leaves = tgt.reverse_leaves(from)
                pos = from
                if not leaves.is_ok then return
                str = leaves.item.str
                make_substring
        end

        fun make_substring
        do
                if pos >= (leaves.index + str.length - 1) then return
                str = str.substring(0, (pos - leaves.index + 1))
        end

        redef fun is_ok do return leaves.is_ok

        redef fun item do
                assert is_ok
                return str
        end

        redef fun index do return pos

        redef fun next do
                pos -= str.length
                leaves.next
                if not leaves.is_ok then return
                str = leaves.item.str
                make_substring
        end
end

private class ReverseRopeCharIterator
        super IndexedIterator[Char]

        var substrs: IndexedIterator[Text]

        var pos: Int

        var subiter: IndexedIterator[Char]

        init(tgt: Rope, from: Int)
        do
                substrs = tgt.reverse_substrings_from(from)
                if not substrs.is_ok then
                        pos = -1
                        return
                end
                subiter = substrs.item.chars.reverse_iterator
                pos = from
        end

        redef fun is_ok do return pos >= 0

        redef fun item do
                assert is_ok
                return subiter.item
        end

        redef fun index do return pos

        redef fun next do
                pos -= 1
                if subiter.is_ok then subiter.next
                if not subiter.is_ok then
                        if substrs.is_ok then substrs.next
                        if substrs.is_ok then subiter = substrs.item.chars.reverse_iterator
                end
        end
end