ListView = {
    backingList = {},
    length = 0,
    paginationPos = 1,
    frame = term.current(),
    drawEntry = nil,
}

function ListView:new(o)
    o = o or {}
    setmetatable(o, self)
    self.__index = self
    return o
end

function ListView:redrawEntry(idx)
    local tw, th = self.frame.getSize()
    if idx >= self.paginationPos and idx-self.paginationPos <= th then
        self.frame.setCursorPos(1, idx-self.paginationPos+1)
        if self.drawEntry then
            self.drawEntry(self.frame, self.backingList[idx])
        else
            self.frame.setBackgroundColor(colors.red)
            self.frame.clearLine()
            self.frame.setBackgroundColor(colors.black)
        end
    end
end

function ListView:itemAt(idx)
    return self.backingList[idx]
end

function ListView:updateItemAt(idx, item)
    self.backingList[idx] = item
    if idx > self.length then
        self.length = idx
    end
    self:redrawEntry(idx)
end

function ListView:clearFrom(idx)
    local tw, th = self.frame.getSize()
    for j = self.length, idx, -1 do
        self.backingList[j] = nil
    end
    self.length = idx-1
    for y = idx-self.paginationPos+1, th, 1 do
        self.frame.setCursorPos(1, y)
        self.frame.clearLine()
    end
end

function ListView:redraw()
    if self.drawEntry then
        local tw, th = self.frame.getSize()
        local backingIdx = self.paginationPos
        for idx = 1, th, 1 do
            self.frame.setCursorPos(1, idx)
            if self.backingList[backingIdx] == nil then
                self.frame.clearLine()
            else
                self.drawEntry(self.frame, self.backingList[backingIdx])
            end
            backingIdx = backingIdx + 1
        end
    else
        self.frame.setBackgroundColor(colors.red)
        self.frame.clear()
        self.frame.setBackgroundColor(colors.black)
    end
end

function ListView:updatePage(scrollPos)
    if scrollPos ~= self.paginationPos then
        self.paginationPos = scrollPos
        self:redraw()
    end
end

function ListView:updatePartial(filter)
    if self.drawEntry then
        local tw, th = self.frame.getSize()
        local backingIdx = self.paginationPos
        for idx = 1, th, 1 do
            self.frame.setCursorPos(1, idx)
            if self.backingList[backingIdx] ~= nil and filter(self.backingList[backingIdx]) then
                self.self.drawEntry(self.self.frame, self.backingList[backingIdx])
            end
            backingIdx = backingIdx + 1
        end
    end
end


return ListView