--- @class ShadowcasterBehavior : Behavior
local behavior = {}
behavior.id = "shadowcaster"
behavior.__index = behavior

function behavior.new() return setmetatable({}, behavior) end

local function makeGradientMesh(w, h, topColor, bottomColor)
    local vertices = {
        { 0,           0, 0, 0, topColor[1],    topColor[2],    topColor[3],    topColor[4] },    -- левый верх
        { w,           0, 1, 0, topColor[1],    topColor[2],    topColor[3],    topColor[4] },    -- правый верх
        { w + w * 0.1, h, 1, 1, bottomColor[1], bottomColor[2], bottomColor[3], bottomColor[4] }, -- правый низ
        { 0 - w * 0.1, h, 0, 1, bottomColor[1], bottomColor[2], bottomColor[3], bottomColor[4] }, -- левый низ
    }
    local mesh = love.graphics.newMesh(vertices, "fan", "static")
    return mesh
end

local function getFakeShadow(r)
    local pi = math.pi

    if r <= pi / 4 then
        -- 1
        return false, 1
    end
    if r <= pi / 2 then
        -- 2
        return true, 1 - (r - pi / 4) / (pi / 4)
    end
    if r <= 3 * pi / 4 then
        -- 3
        return true, (r - pi / 2) / (pi / 4)
    end
    if r <= 5 * pi / 4 then
        -- 4
        return false, 1
    end
    if r <= 3 * pi / 2 then
        -- 5
        return true, 1 - (r - 5 * pi / 4) / (pi / 4)
    end
    if r <= 7 * pi / 4 then
        -- 6
        return true, (r - 3 * pi / 2) / (pi / 4)
    end
    -- 1
    return false, 1
end

function behavior:draw()
    local sprite = self.owner:has(Tree.behaviors.sprite)
    local map = self.owner:has(Tree.behaviors.map)
    if not map then return end

    local ppm = Tree.level.camera.pixelsPerMeter
    local position = map.displayedPosition + Vec3 { 0.5, 0.5 }

    love.graphics.setCanvas(Tree.level.render.shadowLayer)
    love.graphics.push()
    love.graphics.scale(ppm)
    love.graphics.setColor(0, 0, 0, 0.5)
    love.graphics.translate(position.x, position.y)
    love.graphics.ellipse("fill", 0, 0, 0.2, 0.2 * math.cos(math.pi / 4))

    if not sprite then
        love.graphics.pop()
        return
    end

    local r = love.timer.getTime() % (2 * math.pi)

    local drawFakeShadow, opacity = getFakeShadow(r)
    local nangle = (math.pi + r) % (2 * math.pi)
    love.graphics.rotate(nangle)

    love.graphics.setColor(0, 0, 0, math.min(opacity * opacity, 0.5))
    sprite.animationTable[sprite.state]:draw(Tree.assets.files.sprites.character[sprite.state],
        0,
        0, nil, ((nangle >= math.pi / 2 and nangle < (3 * math.pi / 2)) and -1 or 1) / ppm * sprite.side,
        1.2 / ppm,
        38, 47)

    if drawFakeShadow then
        love.graphics.setColor(0, 0, 0, 1)
        local mesh = makeGradientMesh(0.4, 1, { 0, 0, 0, 0.15 },
            { 0, 0, 0, 0.0 })
        love.graphics.push()
        love.graphics.rotate(math.pi)
        love.graphics.translate(-0.2, 0)
        love.graphics.draw(mesh)
        love.graphics.pop()
    end
    love.graphics.pop()
    love.graphics.setColor(1, 1, 1)
    love.graphics.setCanvas()
end

return behavior