local gl   = honey.gl
local glfw = honey.glfw
local ode  = honey.ode

local ecs       = require 'honey.ecs.ecs'
local collision = require 'honey.ecs.collision'
local node      = require 'honey.ecs.node'

local image  = require 'honey.asset.image'
local shader = require 'honey.asset.shader'
local mesh   = require 'honey.asset.mesh'

local glm = require 'honey.glm'
local Vec3       = glm.Vec3
local Mat4       = glm.Mat4


local module = {}
setmetatable(module, {__index=_G})
setfenv(1, module)



local function drawMesh(program, uniforms, matrices, vao, count)
	gl.UseProgram(program)

	-- bind matrices
	shader.configure(program, {
		matrix={
			model = matrices.model,
			view = matrices.view,
			projection = matrices.projection,
		},
	})

	-- bind textures
	local offset = 0
	for name, tbl in pairs(uniforms.textures or {}) do
		local tex = image.get(tbl.filename)
		gl.BindTexture(gl.TEXTURE_2D + offset, tex)
		shader.setInt(program, name, offset)
		offset = offset+1
	end

	-- configure additional uniforms
	shader.configure(program, uniforms)

	-- render mesh
	gl.BindVertexArray(vao)
	gl.DrawElements(gl.TRIANGLES, count, gl.UNSIGNED_INT, 0)
end


local function drawMeshes(db, view, projection)
	local meshes = db:queryComponent("renderMesh")
	for id, tbl in pairs(meshes) do
		-- get model matrix
		local node = db:getComponent(id, "node")
		local model = (node and node._matrix) or Mat4():identity()

		-- get shader program
		local program = shader.get(tbl.shader)

		-- get mesh
		local vao, count = mesh.get(tbl.mesh.filename, tbl.mesh.index)

		-- draw c:
		drawMesh(program, tbl.uniforms or {}, {view=view, model=model, projection=projection}, vao, count)
	end
end


local function drawGeoms(db, view, projection)
	-- draw wireframes
	gl.Enable(gl.CULL_FACE)
	gl.PolygonMode(gl.FRONT_AND_BACK, gl.LINE)
	gl.LineWidth(1)

	-- shader program for all geoms
	local program = shader.get{ vertex="builtin.basic3d.vert", fragment="builtin.color.frag" }
	local uniforms = {
		vec3 = {
			color = Vec3{ 1, 0, 1 },
		},
	}

	local query = db:queryComponent("collision")
	for id, tbl in pairs(query) do
		-- compute model matrix
		local m = Mat4():identity()
		m[1][4], m[2][4], m[3][4] = ode.GeomGetPosition(tbl._geom)
		m[1][1], m[1][2], m[1][3],
		m[2][1], m[2][2], m[2][3],
		m[3][1], m[3][2], m[3][3] = ode.GeomGetRotation(tbl._geom)

		local matrices = {
			view=view,
			projection=projection,
			model=m,
		}

		-- get the mesh
		if tbl.class == "sphere" then
			m:scale(Vec3{tbl.radius, tbl.radius, tbl.radius})
			local vao, count = mesh.get("builtin.hemisphere", 1)
			drawMesh(program, uniforms, matrices, vao, count)
			m:rotateX(math.pi)
			drawMesh(program, uniforms, matrices, vao, count)
		elseif tbl.class == "box" then
			m:scale(Vec3{tbl.lx, tbl.ly, tbl.lz})
			local vao, count = mesh.get("builtin.cube", 1)
			drawMesh(program, uniforms, matrices, vao, count)
		elseif tbl.class == "capsule" then
			m:scale(Vec3{tbl.radius, tbl.length/2, tbl.radius})
			local vao, count = mesh.get("builtin.tube", 1)
			drawMesh(program, uniforms, matrices, vao, count)
			m:scale(Vec3{1, 2*tbl.radius/tbl.length, 1})
				:translate(Vec3{0, tbl.length/2, 0})
			vao, count = mesh.get("builtin.hemisphere", 1)
			drawMesh(program, uniforms, matrices, vao, count)
			m:translate(Vec3{0, -tbl.length, 0})
				:rotateX(math.pi)
			drawMesh(program, uniforms, matrices, vao, count)
		elseif tbl.class == "ray" then
			m:scale(Vec3{0.001, 0.001, tbl.length})
			local vao, count = mesh.get("builtin.cube", 1)
			drawMesh(program, uniforms, matrices, vao, count)
		end
	end

	-- switch out of wireframe mode
	gl.PolygonMode(gl.FRONT_AND_BACK, gl.FILL)
end


local render = ecs.System("render", function(db, dt, p)
	for id, camera in pairs(db:queryComponent("camera")) do
		-- get camera's view and projection matrices
		local projection = camera.projection
		local view = Mat4()
		local node = db:getComponent(id, "node")
		if node then
			honey.glm.mat4_inv(node._matrix.data, view.data)
		else
			view:identity()
		end

		-- optionally draw collision geoms
		if p.drawGeoms then
			drawGeoms(db, view, projection)
		end
		
		-- render all scene meshes
		drawMeshes(db, view, projection)
	end
end)
render:addDependencies(node.system)
render:addDependencies(collision.system)

system = {render}


return module