gameutils

--[[
    GameUtil
    An API for drawing sprites and animations made in NPaintPro
    By NitrogenFingers
]]--


--The back buffer. Initialized as nil
local backbuffer = nil
--The bounds of the terminal the back buffer displays to
local tw,th = nil, nil

--[[Constructs a new buffer. This must be done before the buffer can written to.
    Params: terminal:?table = The function table to draw to a screen. By default (nil) this refers
            to the native terminal, but monitor displays can be passed through as well:
            local leftMonitor = peripherals.wrap("left")
            initializeBuffer(leftMonitor)
    Returns:boolean = True if the buffer was successfully initialized; false otherwise
]]--
function initializeBuffer(terminal)
    if not terminal then terminal = term end
    if not terminal.getSize then
        error("Parameter cannot be used to initialize the backbuffer.")
    end
    if not terminal.isColour() then
        error("Parameter does not represent an advanced computer.")
    end

    tw,th = terminal.getSize()
    backbuffer = { }
    for y=1,th do
        backbuffer[y] = { }
    end
    return true
end

--[[Will clear the buffer and reset to nil, or to a colour if provided
    Params: colour:?number = The colour to set the back buffer to
    Returns:nil
]]--
function clearBuffer(colour)
    if not backbuffer then
        error("Back buffer not yet initialized!")
    end

    for y=1,#backbuffer do
        backbuffer[y] = { }
        if colour then
            for x=1,tw do
                backbuffer[y][x] = colour
            end
        end
    end
end

--[[Draws the given entity to the back buffer
    Params: entity:table = the entity to draw to the buffer
    Returns:nil
]]--
function writeToBuffer(entity)
    if not backbuffer then
        error("Back buffer not yet initialized!")
    end

    local image = nil
    if entity.type == "animation" then
        image = entity.frames[entity.currentFrame]
    else
        image = entity.image
    end

    for y=1,image.dimensions.height do
        for x=1,image.dimensions.width do
            if image[y][x] then
                local xpos,ypos = x,y
                if entity.mirror.x then xpos = image.dimensions.width - x + 1 end
                if entity.mirror.y then ypos = image.dimensions.height - y + 1 end

                --If the YPos doesn't exist, no need to loop through the rest of X!
                --Don't you love optimization?
                if not backbuffer[entity.y + ypos - 1] then break end

                backbuffer[entity.y + ypos - 1][entity.x + xpos - 1] = image[y][x]
            end
        end
    end
end

--[[Draws the contents of the buffer to the screen. This will not clear the screen or the buffer.
    Params: terminal:table = the terminal to draw to
    Returns:nil
]]--
function drawBuffer(terminal)
    if not backbuffer then
        error("Back buffer not yet initialized!")
    end
    if not terminal then terminal = term end
    if not terminal.setCursorPos or not terminal.setBackgroundColour or not terminal.write then
        error("Parameter cannot be used to initialize the backbuffer.")
    end
    if not terminal.isColour() then
        error("Parameter does not represent an advanced computer.")
    end

    for y=1,math.min(#backbuffer, th) do
        for x=1,tw do
            if backbuffer[y][x] then
                terminal.setCursorPos(x,y)
                terminal.setBackgroundColour(backbuffer[y][x])
                terminal.write(" ")
            end
        end
    end
end

--[[Converts a hex digit into a colour value
    Params: hex:?string = the hex digit to be converted
    Returns:string A colour value corresponding to the hex, or nil if the character is invalid
]]--
local function getColourOf(hex)
    local value = tonumber(hex, 16)
    if not value then return nil end
    value = math.pow(2,value)
    return value
end

--[[Converts every pixel of one colour in a given sprite to another colour
    Use for "reskinning". Uses OO function.
    Params: self:sprite = the sprite to reskin
            oldcol:number = the colour to replace
            newcol:number = the new colour
    Returns:nil
]]--
local function repaintS(self, oldcol, newcol)
    for y=1,self.image.bounds.height do
        for x=1, self.image.bounds.width do
            if self.image[y][x] == oldcol then
                self.image[y][x] = newcol
            end
        end
    end
end

--[[Converts every pixel of one colour in a given animation to another colour
    Use for "reskinning". Uses OO function.
    Params: self:animation = the animation to reskin
            oldcol:number = the colour to replace
            newcol:number = the new colour
    Returns:nil
]]--
local function repaintA(self, oldcol, newcol)
    for f=1,#self.frames do
        print(self.frames[f].bounds)
        for y=1,self.frames[f].bounds.height do
            for x=1, self.frames[f].bounds.width do
                if self.frames[f][y][x] == oldcol then
                    self.frames[f][y][x] = newcol
                end
            end
        end
    end
end

--[[Prints the sprite on the screen
    Params: self:sprite = the sprite to draw
    Returns:nil
]]--
local function drawS(self)
    local image = self.image

    for y=1,image.dimensions.height do
        for x=1,image.dimensions.width do
            if image[y][x] then
                local xpos,ypos = x,y
                if self.mirror.x then xpos = image.dimensions.width - x + 1 end
                if self.mirror.y then ypos = image.dimensions.height - y + 1 end

                term.setBackgroundColour(image[y][x])
                term.setCursorPos(self.x + xpos - 1, self.y + ypos - 1)
                term.write(" ")
            end
        end
    end
end

--[[Prints the current frame of the animation on screen
    Params: self:anim = the animation to draw
            frame:?number = the specific frame to draw (default self.currentFrame)
    Returns:nil
]]--
local function drawA(self, frame)
    if not frame then frame = self.currentFrame end
    local image = self.frames[frame]

    for y=1,image.dimensions.height do
        for x=1,image.dimensions.width do
            if image[y][x] then
                local xpos,ypos = x,y
                if self.mirror.x then xpos = image.dimensions.width - x + 1 end
                if self.mirror.y then ypos = image.dimensions.height - y + 1 end

                term.setBackgroundColour(image[y][x])
                term.setCursorPos(self.x + xpos - 1, self.y + ypos - 1)
                term.write(" ")
            end
        end
    end
end

--[[Checks the animation timer provided to see whether or not the animation needs to be updated.
    If so, it makes the necessary change.
    Params: self:animation = the animation to be updated
            timerID:number = the ID of the most recent timer event
    Returns:bool = true if the animation was update; false otherwise
]]--
local function updateA(self, timerID)
    if self.timerID and timerID and self.timerID == timerID then
        self.currentFrame = self.currentFrame + 1
        if self.currentFrame > self.upperBound then
            self.currentFrame = self.lowerBound
        end
        return true
    else
        return false
    end
end

--[[Moves immediately to the next frame in the sequence, as though an update had been called.
    Params: self:animation = the animation to update
    Returns:nil
]]--
local function nextA(self)
    self.currentFrame = self.currentFrame + 1
    if self.currentFrame > self.upperBound then
        self.currentFrame = self.lowerBound
    end
end

--[[Moves immediately to the previous frame in the sequence
    Params: self:animation = the animation to update
    Returns:nil
]]--
local function previousA(self)
    self.currentFrame = self.currentFrame - 1
    if self.currentFrame < self.lowerBound then
        self.currentFrame = self.upperBound
    end
end

--[[A simple debug function that displays the outline of the bounds
    on a given shape. Useful when testing collision detection or other game
    features.
    Params: entity:table = the bounded entity to represent
            colour:?number = the colour to draw the rectangle (default red)
    Returns:nil
]]--
local function drawBounds(entity, colour)
    if not colour then colour = colours.red end
    local image = nil
    if entity.type == "animation" then image = entity.frames[entity.currentFrame]
    else image = entity.image end

    term.setBackgroundColour(colour)

    corners = {
        topleft = { x = entity.x + image.bounds.x - 1, y = entity.y + image.bounds.y - 1 };
        topright = { x = entity.x + image.bounds.x + image.bounds.width - 2, y = entity.y + image.bounds.y - 1 };
        botleft = { x = entity.x + image.bounds.x - 1, y = entity.y + image.bounds.y + image.bounds.height - 2 };
        botright = { x = entity.x + image.bounds.x + image.bounds.width - 2, y = entity.y + image.bounds.y + image.bounds.height - 2 };
    }

    term.setCursorPos(corners.topleft.x, corners.topleft.y)
    term.write(" ")
    term.setCursorPos(corners.topright.x, corners.topright.y)
    term.write(" ")
    term.setCursorPos(corners.botleft.x, corners.botleft.y)
    term.write(" ")
    term.setCursorPos(corners.botright.x, corners.botright.y)
    term.write(" ")
end

--[[Creates a bounding rectangle object. Used in drawing the bounds and the rCollidesWith methods
    Params: self:table = the entity to create the rectangle
    Returns:table = the left, right, top and bottom edges of the rectangle
]]--
local function createRectangle(entity)
    local image = nil
    if entity.type == "animation" then
        image = entity.frames[entity.currentFrame]
    else
        image = entity.image
    end
    --Note that the origin is always 1, so we subtract 1 for every absolute coordinate we have to test.
    return {
        left = entity.x + image.bounds.x - 1;
        right = entity.x + image.bounds.x + image.bounds.width - 2;
        top = entity.y + image.bounds.y - 1;
        bottom = entity.y + image.bounds.y + image.bounds.height - 2;
    }
end

--[[Performs a rectangle collision with another given entity. Entity can be of sprite or animation
    type (also true of the self). Bases collision using a least squared approach (rectangle precision).
    Params: self:sprite,animation = the object in question of the testing
            other:sprite,animation = the other object tested for collision
    Returns:bool = true if bounding rectangle intersect is true; false otherwse
]]--
local function rCollidesWith(self, other)
    --First we construct the rectangles
    local img1C, img2C = createRectangle(self), createRectangle(other)

    --We then determine the "relative position" , in terms of which is farther left or right
    leftmost,rightmost,topmost,botmost = nil,nil,nil,nil
    if img1C.left < img2C.left then
        leftmost = img1C
        rightmost = img2C
    else
        leftmost = img2C
        rightmost = img1C
    end
    if img1C.top < img2C.top then
        topmost = img1C
        botmost = img2C
    else
        topmost = img2C
        botmost = img1C
    end

    --Then we determine the distance between the "extreme" edges-
        --distance between leftmost/right edge and rightmost/left edge
        --distance between topmost/bottom edge and bottommost/top edge
    local xdist = rightmost.left - leftmost.right
    local ydist = botmost.top - topmost.bottom

    --If both are negative, our rectangles intersect!
    return xdist <= 0 and ydist <= 0
end

--[[Performs a pixel collision test on another given entity. Either entity can be of sprite or animation
    type. This is done coarsegrain-finegrain, we first find the intersection between the rectangles
    (if there is one), and then test the space within that intersection for any intersecting pixels.
    Params: self:sprite,animation = the object in question of the testing
            other:sprite,animation = the other object being tested for collision
    Returns:?number,?number: The X and Y position in which the collision occurred.
]]--
local function pCollidesWith(self, other)
    --Identically to rCollidesWith, we create our rectangles...
    local img1C, img2C = createRectangle(self), createRectangle(other)
    --We'll also need the images to compare pixels later
    local img1, img2 = nil,nil
    if self.type == "animation" then img1 = self.frames[self.currentFrame]
    else img1 = self.image end
    if other.type == "animation" then img2 = other.frames[other.currentFrame]
    else img2 = other.image end

    --...then we position them...
    leftmost,rightmost,topmost,botmost = nil,nil,nil,nil
    --We also keep track of which is left and which is right- it doesn't matter in a rectangle
    --collision but it does in a pixel collision.
    img1T,img2T = {},{}

    if img1C.left < img2C.left then
        leftmost = img1C
        rightmost = img2C
        img1T.left = true
    else
        leftmost = img2C
        rightmost = img1C
        img2T.left = true
    end
    if img1C.top < img2C.top then
        topmost = img1C
        botmost = img2C
        img1T.top = true
    else
        topmost = img2C
        botmost = img1C
        img2T.top = true
    end

    --...and we again find the distances between the extreme edges.
    local xdist = rightmost.left - leftmost.right
    local ydist = botmost.top - topmost.bottom

    --If these distances are > 0 then we stop- no need to go any farther.
    if xdist > 0 or ydist > 0 then return false end


    for x = rightmost.left, rightmost.left + math.abs(xdist) do
        for y = botmost.top, botmost.top + math.abs(ydist) do
            --We know a collision has occurred if a pixel is occupied by both images. We do this by
            --first transforming the coordinates based on which rectangle is which, then testing if a
            --pixel is at that point
                -- The leftmost and topmost takes the distance on x and y and removes the upper component
                -- The rightmost and bottommost, being the farther extremes, compare from 1 upwards
            local testX,testY = 1,1
            if img1T.left then testX = x - img1C.left + 1
            else testX = x - img1C.left + 1 end
            if img1T.top then testY = y - img1C.top + 1
            else testY = y - img1C.top + 1 end

            local occupy1 = img1[testY + img1.bounds.y-1][testX + img1.bounds.x-1] ~= nil

            if img2T.left then testX = x - img2C.left + 1
            else testX = x - img2C.left + 1 end
            if img2T.top then testY = y - img2C.top + 1
            else testY = y - img2C.top + 1 end

            local occupy2 = img2[testY + img2.bounds.y-1][testX + img2.bounds.x-1] ~= nil

            if occupy1 and occupy2 then return true end
        end
    end
    --If the looop terminates without returning, then no pixels overlap
    return false
end

--[[Moves the sprite or animation to the specified coordinates. This performs the auto-centering, so
    the user doesn't have to worry about adjusting for the bounds of the shape. Recommended for absolute
    positioning operations (as relative direct access to the X will have unexpected results!)
    Params: self:table = the animation or sprite to move
    x:number = the new x position
    y:number = the new y position
]]--
local function moveTo(self, x, y)
    local image = nil
    if self.type == "animation" then
        image = self.frames[self.currentFrame]
    else
        image = self.image
    end

    self.x = x - image.bounds.x + 1
    self.y = y - image.bounds.y + 1
end

--[[
    Sprites Fields:
x:number = the x position of the sprite in the world
y:number = the y position of the sprite in the world
image:table = a table of the image. Indexed by height, a series of sub-tables, each entry being a pixel
        at [y][x]. It also contains:
    bounds:table =
        x:number = the relative x position of the bounding rectangle
        y:number = the relative y position of the bounding rectangle
        width:number = the width of the bounding rectangle
        height:number = the height of the bounding rectangle
    dimensions:table =
        width = the width of the entire image in pixels
        height = the height of the entire image in pixels

mirror:table =
    x:bool = whether or not the image is mirrored on the X axis
    y:bool = whether or not the image is mirrored on the Y axis
repaint:function = see repaintS (above)
rCollidesWith:function = see rCollidesWith (above)
pCollidesWith:function = see pCollidesWith (above)
draw:function = see drawS (above)
]]--

--[[Loads a new sprite into a table, and returns it to the user.
    Params: path:string = the absolute path to the desired sprite
    x:number = the initial X position of the sprite
    y:number = the initial Y position of the sprite
]]--
function loadSprite(path, x, y)
    local sprite = {
        type = "sprite",
        x = x,
        y = y,
        image = { },
        mirror = { x = false, y = false }
    }

    if fs.exists(path) then
        local file = io.open(path, "r" )
        local leftX, rightX = math.huge, 0
        local topY, botY = nil,nil

        local lcount = 0
        for line in file:lines() do
            lcount = lcount+1
            table.insert(sprite.image, {})
            for i=1,#line do
                if string.sub(line, i, i) ~= " " then
                    leftX = math.min(leftX, i)
                    rightX = math.max(rightX, i)
                    if not topY then topY = lcount end
                    botY = lcount
                end
                sprite.image[#sprite.image][i] = getColourOf(string.sub(line,i,i))
            end
        end
        file:close()

        sprite.image.bounds = {
            x = leftX,
            width = rightX - leftX + 1,
            y = topY,
            height = botY - topY + 1
        }
        sprite.image.dimensions = {
            width = rightX,
            height = botY
        }

        sprite.x = sprite.x - leftX + 1
        sprite.y = sprite.y - topY + 1

        sprite.repaint = repaintS
        sprite.rCollidesWith = rCollidesWith
        sprite.pCollidesWith = pCollidesWith
        sprite.draw = drawS
        sprite.moveTo = moveTo
        return sprite
    else
        error(path.." not found!")
    end
end

--Animations contain
    --Everything a sprite contains, but the image is a series of frames, not just one image
    --An timerID that tracks the last animation
    --An upper and lower bound on the active animation
    --An update method that takes a timer event and updates the animation if necessary

--[[

]]--
function loadAnimation(path, x, y, currentFrame)
    local anim = {
        type = "animation",
        x = x,
        y = y,
        frames = { },
        mirror = { x = false, y = false },
        currentFrame = currentFrame
    }

    table.insert(anim.frames, { })
    if fs.exists(path) then
        local file = io.open(path, "r")
        local leftX, rightX = math.huge, 0
        local topY, botY = nil,nil

        local lcount = 0
        for line in file:lines() do
            lcount = lcount+1
            local cFrame = #anim.frames
            if line == "~" then
                anim.frames[cFrame].bounds = {
                    x = leftX,
                    y = topY,
                    width = rightX - leftX + 1,
                    height = botY - topY + 1
                }
                anim.frames[cFrame].dimensions = {
                    width = rightX,
                    height = botY
                }
                table.insert(anim.frames, { })
                leftX, rightX = math.huge, 0
                topY, botY = nil,nil
                lcount = 0
            else
                table.insert(anim.frames[cFrame], {})
                for i=1,#line do
                    if string.sub(line, i, i) ~= " " then
                        leftX = math.min(leftX, i)
                        rightX = math.max(rightX, i)
                        if not topY then topY = lcount end
                        botY = lcount
                    end
                    anim.frames[cFrame][#anim.frames[cFrame]] [i] = getColourOf(string.sub(line,i,i))
                end
            end
        end
        file:close()
        local cFrame = #anim.frames
        anim.frames[cFrame].bounds = {
            x = leftX,
            y = topY,
            width = rightX - leftX + 1,
            height = botY - topY + 1
        }
        anim.frames[cFrame].dimensions = {
            width = rightX,
            height = botY
        }
        anim.x = anim.x - leftX + 1
        anim.y = anim.y - topY + 1

        if not currentFrame or type(currentFrame) ~= "number" or currentFrame < 1 or
                currentFrame > #anim.frames then
            anim.currentFrame = 1
        end

        anim.timerID = nil
        anim.lowerBound = 1
        anim.upperBound = #anim.frames
        anim.updating = false

        anim.repaint = repaintA
        anim.rCollidesWith = rCollidesWith
        anim.pCollidesWith = pCollidesWith
        anim.draw = drawA
        anim.update = updateA
        anim.next = nextA
        anim.previous = previousA
        anim.moveTo = moveTo
        return anim
    else
        error(path.." not found!")
    end
end