OC/cursor

local function range(bottom, top, value, step)
    if ( value + step > top ) then
        return top
    elseif ( value + step < bottom ) then
        return bottom
    end

    return value + step
end

local function isPositive(value)
    return value == math.abs(value)
end

local function isPositive_zero(value)
    return ( value == 0 and 0 ) or value == math.abs(value)
end

local cursor = {}

function cursor.init()
    cursor.absolute = {}
    cursor.absolute.x = 1
    cursor.absolute.y = 1
    cursor.absolute.prev = {}
    cursor.absolute.prev.x = 1
    cursor.absolute.prev.y = 1

    cursor.relative = {}
    cursor.relative.x = 1
    cursor.relative.y = 1
    cursor.relative.prev = {}
    cursor.relative.prev.x = 1
    cursor.relative.prev.y = 1

    cursor.delta = {}
    cursor.delta.x = 0
    cursor.delta.y = 0
    cursor.delta.prev = {}
    cursor.delta.prev.x = 0
    cursor.delta.prev.y = 0

    cursor.space = {}
    cursor.space.lengthX = 1
    cursor.space.lengthY = 1

    --[[
        wall = {
            len_string,
            len_string,
            ...
            len_string
        }
    ]]--
    cursor.space.wall = {}
    cursor.space.freeSpace = true

    cursor.allowMoveX = true
    cursor.allowMoveY = true
end

function cursor.addStringLen(number, position)
    if ( number < 0 ) then
        number = 0
    end

    table.insert( cursor.space.wall, position, number )

    if ( cursor.absolute.x > cursor.space.wall[cursor.absolute.y] ) then
        cursor.moveEnd()
        cursor.calculate()
    end
end

function cursor.removeStringLen(position)
    if ( #cursor.space.wall > 1 ) then
        table.remove( cursor.space.wall, position )

        cursor.absolute.prev.y = cursor.absolute.y
        if ( cursor.onBottom() ) then
            cursor.absolute.y = #cursor.space.wall
        end
        if ( cursor.absolute.x > cursor.space.wall[cursor.absolute.y] ) then
            cursor.moveEnd()
        end
    else
        cursor.space.wall[cursor.absolute.y] = 0
        cursor.moveHome()
    end

    cursor.calculate()
end

function cursor.modifyStringLen_onCursor(number, realtive)
    if ( realtive ) then
        cursor.space.wall[cursor.absolute.y] = cursor.space.wall[cursor.absolute.y] + number
    else
        cursor.space.wall[cursor.absolute.y] = number
    end

    if ( cursor.space.wall[cursor.absolute.y] < 0 ) then
        cursor.space.wall[cursor.absolute.y] = 0
    end

    if ( cursor.absolute.x > cursor.space.wall[cursor.absolute.y] ) then
        cursor.moveEnd()
        cursor.calculate()
    end
end

function cursor.modifyStringLen(number, position, realtive)
    if ( not position ) then
        return nil
    end

    if ( realtive ) then
        cursor.space.wall[position] = cursor.space.wall[position] + number
    else
        cursor.space.wall[position] = number
    end

    if ( cursor.space.wall[cursor.absolute.y] < 0 ) then
        cursor.space.wall[cursor.absolute.y] = 0
    end

    if ( cursor.absolute.x > cursor.space.wall[cursor.absolute.y] ) then
        cursor.moveEnd()
        cursor.calculate()
    end
end

function cursor.onEndLine()
    return cursor.absolute.x == cursor.space.wall[cursor.absolute.y] + 1
end

function cursor.onHomeLine()
    return cursor.absolute.x == 1
end

function cursor.onBottom()
    return cursor.absolute.y >= #cursor.space.wall
end

function cursor.onTop()
    return cursor.absolute.y == 1
end

function cursor.checkLine(step)
    local lineExist = cursor.space.wall[cursor.absolute.y+step] ~= nil
    local lineLessCurrent = nil
    if ( lineExist ) then
        lineLessCurrent = cursor.space.wall[cursor.absolute.y+step] < cursor.space.wall[cursor.absolute.y]
        lineLessCurrent = lineLessCurrent and cursor.absolute.x > cursor.space.wall[cursor.absolute.y+step]
    end

    return lineExist, lineLessCurrent
end

function cursor.calculate()
    cursor.relative.prev.x = cursor.relative.x
    cursor.relative.prev.y = cursor.relative.y
    cursor.relative.x = math.max( math.min(cursor.absolute.x, cursor.space.lengthX), 1 )
    cursor.relative.y = math.max( math.min(cursor.absolute.y, cursor.space.lengthY), 1 )

    cursor.delta.prev.x = cursor.delta.x
    cursor.delta.prev.y = cursor.delta.x
    cursor.delta.x = cursor.absolute.x - cursor.relative.x
    cursor.delta.y = cursor.absolute.y - cursor.relative.y
end

function cursor.set(absolute_x, absolute_y)
    cursor.absolute.prev.x = cursor.absolute.x
    cursor.absolute.prev.y = cursor.absolute.y

    cursor.absolute.x = absolute_x
    cursor.absolute.y = absolute_y

    cursor.calculate()
end

function cursor.move(step_x, step_y)
    local stepY_positive = isPositive_zero(step_y)
    if ( stepY_positive ~= 0 ) then
        local action = ( stepY_positive and cursor.moveEndNextLine ) or cursor.moveEndPrevLine

        local exist, less = cursor.checkLine(step_y)
        if ( exist and less ) then
            action(step_y)
        elseif ( exist ) then
            cursor.absolute.prev.y = cursor.absolute.y
            cursor.absolute.y = cursor.absolute.y + step_y
        end
    end

    local stepX_positive = isPositive_zero(step_x)
    if ( stepX_positive == true and cursor.onEndLine() and not cursor.onBottom() ) then
        cursor.absolute.prev.y = cursor.absolute.y
        cursor.absolute.y = cursor.absolute.y + 1
        cursor.moveHome()
    elseif ( stepX_positive == false and cursor.onHomeLine() and not cursor.onTop() ) then
        cursor.absolute.prev.y = cursor.absolute.y
        cursor.absolute.y = cursor.absolute.y - 1
        cursor.moveEnd()
    elseif ( stepX_positive ~= 0 ) then
        cursor.absolute.prev.x = cursor.absolute.x
        cursor.absolute.x = range(1, cursor.space.wall[cursor.absolute.y] + 1, cursor.absolute.x, step_x)
    end

    cursor.calculate()
end

function cursor.moveHome()
    if ( cursor.space.wall[cursor.absolute.y] ) then
        cursor.absolute.prev.x = cursor.absolute.x
        cursor.absolute.x = 1
    end
end

function cursor.moveEnd()
    if ( cursor.space.wall[cursor.absolute.y] ) then
        cursor.absolute.prev.x = cursor.absolute.x
        cursor.absolute.x = cursor.space.wall[cursor.absolute.y] + 1
    end
end

function cursor.moveEndNextLine(step)
    if ( cursor.space.wall[cursor.absolute.y+step] ) then
        cursor.absolute.prev.y = cursor.absolute.y
        cursor.absolute.y = cursor.absolute.y + step

        cursor.absolute.prev.x = cursor.absolute.x
        cursor.absolute.x = cursor.space.wall[cursor.absolute.y] + 1
    end
end

function cursor.moveEndPrevLine(step)
    if ( cursor.space.wall[cursor.absolute.y+step] ) then
        cursor.absolute.prev.y = cursor.absolute.y
        cursor.absolute.y = cursor.absolute.y + step

        cursor.absolute.prev.x = cursor.absolute.x
        cursor.absolute.x = cursor.space.wall[cursor.absolute.y] + 1
    end
end

return cursor