#!/usr/bin/luajit
local smolhershey = require "smolhershey"
local rotate, filename = ...            -- command-line arguments
local font = smolhershey.load(filename or "imlac-pds-1-ssvchr.22.jhf")

local canvas_methods = {}

-- Set a pixel in the canvas.
function canvas_methods.pset(canvas, x, y)
    if canvas[x] == nil then canvas[x] = {} end
    canvas[x][y] = 1
end

local function round(x)
    return math.floor(x + 0.5)
end

-- Default coordinate transformation is identity
function canvas_methods.xform(canvas, x1, y1) return x1, y1 end

-- Draw a line using Amit’s straightforward lerp method from
-- <https://www.redblobgames.com/grids/line-drawing/>.
function canvas_methods.line(canvas, x1, y1, x2, y2)
    x1, y1 = canvas:xform(x1, y1)
    x2, y2 = canvas:xform(x2, y2)

    local Δz = math.max(math.abs(x1 - x2), math.abs(y1 - y2))

    if Δz == 0 then             -- Avoid division by zero errors
        canvas:pset(x1, y1)
        return
    end

    local mx = (x2 - x1) / Δz   -- Slope in X
    local my = (y2 - y1) / Δz   -- Slope in Y
    for z = 0, Δz do
       canvas:pset(round(mx*z + x1), round(my*z + y1))
    end
end

function canvas_methods.draw(canvas)
    local xmin, xmax, ymin, ymax
    for x, col in pairs(canvas) do
        if type(x) ~= "string" then -- handle .xform override case
            if xmin == nil or x < xmin then xmin = x end
            if xmax == nil or x > xmax then xmax = x end
            for y in pairs(col) do
                if ymin == nil or y < ymin then ymin = y end
                if ymax == nil or y > ymax then ymax = y end
            end
        end
    end

    for y = ymin, ymax do
        for x = xmin, xmax do
            if canvas[x] and canvas[x][y] then
                io.write "@@"
            else
                io.write "  "
            end
        end
        io.write "\n"
    end
end

local function canvas()
    return setmetatable({}, {__index = canvas_methods})
end

local cvs = canvas()

if rotate and rotate ~= "-nr" then
   cvs.xform = function (canvas, x, y) return x + y, y - x end
end

local function cvsline(...) cvs:line(...) end
local gc = font:gc(0, 0, cvsline)
local x = gc.cp.x               -- Save X position
gc:show("Hello, Mina")
gc.cp = {x=x, y=gc.cp.y + 28}   -- Move down 28 units
gc:show("{}@&-/\\")
cvs:draw()