-- Prototype:  the menu intro, through to the menu's own backdrop, as one continuous shot.
--
-- An explosion, the Singe dragon and name flying out of it toward the camera, the tagline fading in
-- underneath -- and then the grid rising out of the dark beneath the logo while the smoke is still
-- clearing, the logo lifting away, and the backdrop the menu sits on left running.  It is one scene
-- from start to finish rather than an intro handing over to something else:  there is no cut, and
-- nothing has to be loaded at the join.
--
-- The fire is 3D emitters rather than the 2D ones the fireball prototype used, because the logo has
-- to come out THROUGH it:  2D particles are drawn with the overlay, on top of the whole scene, so
-- the logo would have flown out behind its own explosion.

local BLAST_Z   = -30.0       -- Where the charge goes off.
local BLAST_Y   = 2.5         -- and how high, which is where the logo comes from.
local REST_Z    = -8.0        -- Where the logo ends up.
local CAM_Z     = 2.0
local FLY_START = 0.30        -- Seconds:  the logo leaves the blast.
local FLY_END   = 1.90        -- and has settled.
local TAG_START = 2.10        -- The tagline begins to appear.
local TAG_END   = 3.00
local SPINS     = 2.0         -- Turns the logo makes on the way out.
local IDLE_TURN = 7.0         -- Degrees it drifts either side once it has settled.
local IDLE_RATE = 0.9         -- Radians a second of that drift.
local GRID_UP   = 4.30        -- Seconds:  the grid starts to come up out of the dark.
local GRID_LIT  = 5.60        -- and is fully lit.
local LIFT_FROM = 5.90        -- The logo starts to leave.
local LIFT_TO   = 7.30        -- and is gone;  the menu has the screen from here.
local LIFT_RISE = 13.0        -- World units it climbs on the way out.

-- The backdrop, which is the grid the menu sits on.  Same numbers as testScripts/gridBackground.
local CELL      = 6.0
local LINE_W    = 0.12
local CROSS_W   = 0.18
local SPREAD    = 16.0
local HALF_X    = 12
local DEPTH     = 14
local GRID_SPEED = 9.0
local FOG_R     = 8
local FOG_G     = 3
local FOG_B     = 20
local FOG_NEAR  = 12
local FOG_FAR   = 72
local SUN_R     = 10.5
local SUN_Y     = 7.6
local SUN_Z     = -34.0
local SUN_SLICES = 6
local SUN_SEGMENTS = 72
local HORIZ_W   = 70.0
local HORIZ_H   = 0.5
local HORIZ_Z   = -38.0
local HORIZ_D   = 2.2
local CAM_Y     = 2.7         -- Eye height, shared by the logo and the grid:  the backdrop's
                              -- perspective is tuned to it, and at the intro's old 1.2 the grid came
                              -- up flattened with its nearest line a slab across the bottom.
local LOGO_Y    = 2.5         -- Where the logo settles, so it sits on the horizon the grid runs to.

-- The dragon carries no animation, but util/dragonModel.py builds it out of named parts -- head,
-- neck, wingL, wingR and the rest -- and every one of them is its own node.  They all sit at the
-- model's origin though, so turning a wing node would swing the wing round the dragon's middle
-- rather than its shoulder.  The joints are baked into the model now;  coordinates below are the
-- model's own:  it faces +X, +Y is up, and the wings reach out along +/-Z.
local MOUTH        = { 3.55, 5.60, 0.00 }   -- Where the flame leaves, in model coordinates.
local HEAD_AT      = { 0.62, 5.69, 0.00 }   -- The head's baked joint;  see assets/DragonPivots.json.
local FLAP_MAX     = 34.0     -- Degrees a wing rises and falls.
local FLAP_FAST    = 13.0     -- Radians a second while it is flying out of the blast.
local FLAP_SLOW    = 3.4      -- and once it has settled.
local REAR_BACK    = 3.05     -- Seconds:  the head starts to rear.
local REAR_TOP     = 3.40     -- fully back.
local REAR_STRIKE  = 3.58     -- and thrown forward.
local BREATH_START = 3.46
local BREATH_END   = 4.35
local REAR_DONE    = 4.90     -- Back to where it started.
local REAR_ANGLE   = 34.0     -- Degrees the head tips back.
local STRIKE_ANGLE = -14.0    -- and forward through the strike.
local DRAGON_YAW   = -32.0    -- The dragon alone is turned toward the camera, so the wingbeat is
                              -- seen three quarters on rather than edge on;  the name stays square
                              -- to the camera because it has to be read.
local TAGLINE   = "SINGE Is Not a Game Emulator"

local SHOT_TIMES = { 0.25, 1.45, 3.00, 3.60, 4.20, 4.70, 5.10, 5.60, 6.10, 6.60, 7.10, 7.60 }

local font   = fontLoad("Singe/FreeSansBold.ttf", 30)
local frames = 0
local shotAt = 1

overlaySetResolution(720, 480)
fontSelect(font)
fontQuality(FONT_QUALITY_BLENDED)

sceneEnable(true)
sceneSetBackground(0, 0, 0, 255)
sceneSetAmbient(14, 12, 16)
sceneSetBloom(1.2, 0.22)
sceneSetTonemap(TONEMAP_ACES)


-- The dragon's parts carry their own joints now:  util/objToGlb.py bakes them from
-- assets/DragonPivots.json, so wingL turns at the shoulder and head at the top of the neck without
-- anything being rigged here.  This used to build them at run time from bounding boxes, which
-- worked but left every future use of the model to re-derive the same thing.
local function joint(root, name, parent)
	local part = nodeFind(name, root)

	if (part ~= nil) and (parent ~= nil) then
		local px, py, pz = nodeGetPosition(part)
		local qx, qy, qz = nodeGetPosition(parent)

		-- Both parts carry their own baked joint, measured from the model's origin.  Hanging one
		-- off the other makes the child's offset count from the parent's, so the two would add up
		-- and the head would fly off above the neck -- which is exactly what it did.
		nodeSetParent(part, parent)
		nodeSetPosition(part, px - qx, py - qy, pz - qz)
	end

	return part
end


-- Eases in:  slow to start, quick away.  The logo leaves this way so the move begins as a drift.
local function easeIn(t)
	return t * t * t
end


-- Eases out:  fast off the mark, slow into the stop.
local function easeOut(t)
	return 1 - (1 - t) * (1 - t) * (1 - t)
end


-- How far through a span the time is, 0 before it and 1 after.
local function span(t, from, to)
	return math.max(math.min((t - from) / (to - from), 1), 0)
end


local blast = nodeNew()
nodeSetPosition(blast, 0, BLAST_Y, BLAST_Z)

local smoke = emitterNew(blast)
emitterSetMax(smoke, 400)
emitterSetBlend(smoke, PARTICLE_ALPHA)
emitterSetRadius(smoke, 1.6)
emitterSetSpread(smoke, 360)
emitterSetSpeed(smoke, 2.5, 9.0)
emitterSetDrag(smoke, 1.3)
emitterSetGravity(smoke, 0, 3.2, 0)
emitterSetLife(smoke, 1.2, 2.4)
emitterSetSize(smoke, 3.2, 12.0)
emitterSetSpin(smoke, -40, 40)
emitterSetColor(smoke, 64, 46, 38, 170, 10, 9, 12, 0)

local core = emitterNew(blast)
emitterSetMax(core, 500)
emitterSetBlend(core, PARTICLE_ADD)
emitterSetRadius(core, 1.1)
emitterSetSpread(core, 360)
emitterSetSpeed(core, 5.0, 20.0)
emitterSetDrag(core, 1.7)
emitterSetGravity(core, 0, 5.0, 0)
emitterSetLife(core, 0.6, 1.3)
emitterSetSize(core, 2.0, 8.2)
emitterSetColor(core, 255, 232, 150, 255, 190, 35, 0, 0)

local flash = emitterNew(blast)
emitterSetMax(flash, 20)
emitterSetBlend(flash, PARTICLE_ADD)
emitterSetRadius(flash, 0.4)
emitterSetSpread(flash, 360)
emitterSetSpeed(flash, 0, 1.5)
emitterSetLife(flash, 0.10, 0.22)
emitterSetSize(flash, 6.0, 15.0)
emitterSetColor(flash, 255, 255, 235, 255, 255, 150, 40, 0)

local sparks = emitterNew(blast)
emitterSetMax(sparks, 300)
emitterSetBlend(sparks, PARTICLE_ADD)
emitterSetRadius(sparks, 0.5)
emitterSetSpread(sparks, 360)
emitterSetSpeed(sparks, 12.0, 34.0)
emitterSetDrag(sparks, 0.25)
emitterSetGravity(sparks, 0, -15.0, 0)
emitterSetLife(sparks, 0.5, 1.5)
emitterSetSize(sparks, 0.30, 0.05)
emitterSetSpin(sparks, -200, 200)
emitterSetTrail(sparks, 8, 0.10)
emitterSetColor(sparks, 255, 226, 160, 255, 255, 80, 15, 0)

-- The blast's own light, so the logo is lit by the fire it comes out of.
local fireLight = lightNew(LIGHT_POINT)
nodeSetParent(fireLight, blast)
lightSetColor(fireLight, 255, 150, 60)
lightSetRange(fireLight, 60)
lightSetIntensity(fireLight, 0)

-- A key light for the logo once the fire has died, from over the camera's shoulder.
local key = lightNew(LIGHT_DIRECTIONAL)
nodeSetPosition(key, 4, 6, 10)
nodeLookAt(key, 0, 0, REST_Z)
lightSetIntensity(key, 1.15)

-- A magenta rim from behind and to the left, the colour the grid behind the menu is drawn in, so
-- the logo is not a flat white cut-out and the intro and the menu share a palette.
local rim = lightNew(LIGHT_DIRECTIONAL)
nodeSetPosition(rim, -7, 3, REST_Z - 9)
nodeLookAt(rim, 0, 1.5, REST_Z)
lightSetColor(rim, 255, 70, 200)
lightSetIntensity(rim, 2.6)

-- The dragon over the name, assembled the way testScripts/scene30.singe does it.
local logo = nodeNew()
local text = modelInstance(modelLoad("testScripts/Models/SingeText.glb"))
nodeSetParent(text, logo)
local dragon = modelInstance(modelLoad("testScripts/Models/DragonModel.glb"))
nodeSetParent(dragon, logo)
nodeSetPosition(dragon, 0, 4.85, 0)
nodeSetRotation(dragon, 0, DRAGON_YAW, 0)
nodeSetScale(dragon, 0.9)
nodeSetScale(logo, 0.5)
nodeSetVisible(logo, false)

-- The rig.  The head hangs off the neck so that rearing the neck carries the head with it.
local wingLeft = joint(dragon, "wingL")
local wingRite = joint(dragon, "wingR")
local neck     = joint(dragon, "neck")
-- The head hangs off the neck so that rearing the neck carries the head with it.
local head     = joint(dragon, "head", neck)

-- The flame, on a node at the dragon's mouth so it follows the head round.
local jet = nodeNew()

nodeSetParent(jet, head)
-- Relative to the head's own joint, which is where its node now sits.
nodeSetPosition(jet, MOUTH[1] - HEAD_AT[1], MOUTH[2] - HEAD_AT[2], MOUTH[3] - HEAD_AT[3])

-- The flame's own light, so the dragon is lit by what it is breathing.
local breathLight = lightNew(LIGHT_POINT)

nodeSetParent(breathLight, jet)
lightSetColor(breathLight, 255, 160, 60)
lightSetRange(breathLight, 14)
lightSetIntensity(breathLight, 0)

local breath = emitterNew(jet)
emitterSetMax(breath, 400)
emitterSetBlend(breath, PARTICLE_ADD)
emitterSetRadius(breath, 0.05)
emitterSetSpread(breath, 13)
emitterSetSpeed(breath, 4.5, 9.5)
emitterSetDrag(breath, 3.0)
emitterSetLife(breath, 0.28, 0.55)
emitterSetSize(breath, 0.10, 1.30)
emitterSetRate(breath, 260)
emitterSetColor(breath, 255, 244, 200, 255, 235, 60, 0, 0)

-- fontPrint has no centring, so the tagline is measured once through a throwaway sprite and drawn
-- by hand from there;  it is drawn rather than kept as a sprite because a sprite cannot be tinted,
-- and the fade needs the foreground colour's alpha.
local measure = fontToSprite(TAGLINE)
local tagX    = math.floor((overlayGetWidth() - spriteGetWidth(measure)) / 2)
local tagY    = math.floor(overlayGetHeight() * 0.72)

spriteUnload(measure)

-- ===== The backdrop ==========================================================================
--
-- Built now and left unlit.  Bringing it up is a ramp on the emissive colours rather than anything
-- appearing, so the grid rises out of the dark the way a light comes on instead of cutting in.

local function quad(p, i, x0, z0, x1, z1, x2, z2, x3, z3)
	local base = #p / 3

	for _, c in ipairs({ { x0, z0 }, { x1, z1 }, { x2, z2 }, { x3, z3 } }) do
		p[#p + 1] = c[1]
		p[#p + 1] = 0
		p[#p + 1] = c[2]
	end
	for _, n in ipairs({ 1, 2, 3, 1, 3, 4 }) do
		i[#i + 1] = base + n
	end
end


-- A line of constant width thins to nothing as it recedes and breaks into crawling dots;  widening
-- it with distance holds it at about the same width on screen the whole way to the horizon.
local function spread(z)
	return 1 + (-z) / SPREAD
end


-- The height at z that lies on the horizon line, so the bar and the sun's cut land on the same row.
local function horizonY(z)
	return CAM_Y - (CAM_Z - z) * math.tan(math.rad(HORIZ_D))
end


local function gridMesh()
	local p    = {}
	local i    = {}
	local far  = -DEPTH * CELL
	local wide = HALF_X * CELL
	local hN   = LINE_W / 2
	local hF   = hN * spread(far)

	for n = -HALF_X, HALF_X do
		local x = n * CELL

		quad(p, i, x - hN, CELL, x + hN, CELL, x + hF, far, x - hF, far)
	end
	for n = -1, DEPTH do
		local z = -n * CELL
		local h = CROSS_W / 2 * spread(z)

		quad(p, i, -wide, z + h, wide, z + h, wide, z - h, -wide, z - h)
	end

	return meshNew(p, nil, nil, i)
end


-- The sun:  the part of a disc above yClip, as a fan from the middle of the chord.
local function sunMesh(yClip)
	local p  = { 0, yClip, 0 }
	local i  = {}
	local a0 = math.asin(math.max(math.min(yClip / SUN_R, 1), -1))

	for n = 0, SUN_SEGMENTS do
		local a = a0 + (n / SUN_SEGMENTS) * (math.pi - a0 * 2)

		p[#p + 1] = math.cos(a) * SUN_R
		p[#p + 1] = math.sin(a) * SUN_R
		p[#p + 1] = 0
	end
	for n = 1, SUN_SEGMENTS do
		i[#i + 1] = 1
		i[#i + 1] = n + 1
		i[#i + 1] = n + 2
	end

	return meshNew(p, nil, nil, i)
end


-- Unlit, and brought up by their base colour rather than by emissive.  The intro has a key light
-- and a rim for the logo, and a lit material with a black base still catches their specular:  the
-- grid and the sun showed as a grey sheen from the first frame, lit before they were meant to
-- exist.  Unlit takes the lights out of it entirely and the ramp below is the only thing that
-- decides when the backdrop appears.
local gridMat = materialNew()
materialSetColor(gridMat, 0, 0, 0)
materialSetUnlit(gridMat, true)
materialSetDoubleSided(gridMat, true)

local sunMat2 = materialNew()
materialSetColor(sunMat2, 0, 0, 0)
materialSetUnlit(sunMat2, true)
materialSetDoubleSided(sunMat2, true)

local horizMat = materialNew()
materialSetColor(horizMat, 0, 0, 0)
materialSetUnlit(horizMat, true)
materialSetDoubleSided(horizMat, true)

local sliceMat = materialNew()
materialSetColor(sliceMat, FOG_R, FOG_G, FOG_B)
materialSetUnlit(sliceMat, true)
materialSetDoubleSided(sliceMat, true)

local backdrop = nodeNew()
local grid     = nodeNew()

nodeSetMesh(grid, gridMesh(), gridMat)
nodeSetParent(grid, backdrop)

local horizon = nodeNew()
nodeSetMesh(horizon, meshPlane(HORIZ_W * 2, HORIZ_H), horizMat)
nodeSetRotation(horizon, 90, 0, 0)
nodeSetPosition(horizon, 0, horizonY(HORIZ_Z), HORIZ_Z)
nodeSetParent(horizon, backdrop)

local sunCut  = horizonY(SUN_Z) - SUN_Y
local backSun = nodeNew()

nodeSetMesh(backSun, sunMesh(sunCut), sunMat2)
nodeSetPosition(backSun, 0, SUN_Y, SUN_Z)
nodeSetParent(backSun, backdrop)

for n = 1, SUN_SLICES do
	local slice  = nodeNew()
	local height = 0.62 - (n - 1) * 0.07
	local y      = sunCut + 0.5 + (n - 1) * 1.3
	local w      = math.sqrt(math.max(SUN_R * SUN_R - (math.abs(y) + height / 2) ^ 2, 0))

	nodeSetMesh(slice, meshPlane(w * 2, height), sliceMat)
	nodeSetRotation(slice, 90, 0, 0)
	nodeSetPosition(slice, 0, SUN_Y + y, SUN_Z + 0.4)
	nodeSetParent(slice, backdrop)
end


local camera = nodeNew()
nodeSetPosition(camera, 0, CAM_Y, CAM_Z)
cameraSet(camera)


function onOverlayUpdate()
	local t = singeGetTicks() / 1000.0
	local fly = span(t, FLY_START, FLY_END)
	local tag = span(t, TAG_START, TAG_END)

	frames = frames + 1
	if frames == 2 then
		emitterBurst(smoke, 85)
		emitterBurst(core, 110)
		emitterBurst(flash, 5)
		emitterBurst(sparks, 130)
		lightSetIntensity(fireLight, 400)
	end

	-- The fire's light dies over the first second and a half.
	lightSetIntensity(fireLight, 400 * (1 - span(t, 0.05, 1.5)))

	-- The grid comes up out of the dark while the smoke is still clearing, so the two overlap and
	-- there is no moment where one thing has ended and the next has not begun.
	local lit = span(t, GRID_UP, GRID_LIT)

	if (lit > 0) and (lit < 1.0001) then
		materialSetColor(gridMat, 255 * lit, 45 * lit, 190 * lit)
		materialSetColor(horizMat, 255 * lit, 150 * lit, 235 * lit)
		materialSetColor(sunMat2, 255 * lit, 130 * lit, 55 * lit)
		-- The sky stops being black at the same time, or the grid would rise into a void.
		sceneSetBackground(FOG_R * lit, FOG_G * lit, FOG_B * lit, 255)
		sceneSetFog(FOG_R, FOG_G, FOG_B, FOG_NEAR, FOG_FAR)
	end
	if lit > 0 then
		-- Scrolling from the moment it is visible, so it is already alive when it arrives.
		nodeSetPosition(grid, 0, 0, ((t - GRID_UP) * GRID_SPEED) % CELL)
	end

	if fly > 0 then
		local e = easeOut(fly)
		-- Once it has arrived it keeps turning slowly, so the held frame is not a still picture.
		local idle = IDLE_TURN * math.sin((t - FLY_END) * IDLE_RATE) * fly
		local yaw  = 360 * SPINS * (1 - e) + idle

		-- Out of the blast, then up and away once the grid has taken over.  Rising rather than
		-- fading:  a model has no alpha to fade without touching every material it came with.
		local leave = easeIn(span(t, LIFT_FROM, LIFT_TO))

		nodeSetVisible(logo, leave < 1)
		nodeSetPosition(logo, 0, LOGO_Y * e + LIFT_RISE * leave, BLAST_Z + (REST_Z - BLAST_Z) * e)
		nodeSetRotation(logo, 0, yaw, 0)

		-- Wings:  beating hard on the way out, easing to a hover once it has arrived.
		local rate = FLAP_FAST + (FLAP_SLOW - FLAP_FAST) * e
		local flap = FLAP_MAX * math.sin(t * rate)

		nodeSetRotation(wingLeft, -flap, 0, 0)
		nodeSetRotation(wingRite, flap, 0, 0)

		-- The head rears back, snaps forward, and settles;  the flame goes with the strike.
		local pitch = 0

		if t < REAR_TOP then
			pitch = REAR_ANGLE * span(t, REAR_BACK, REAR_TOP)
		elseif t < REAR_STRIKE then
			local k = span(t, REAR_TOP, REAR_STRIKE)

			pitch = REAR_ANGLE + (STRIKE_ANGLE - REAR_ANGLE) * k
		else
			pitch = STRIKE_ANGLE * (1 - easeOut(span(t, REAR_STRIKE, REAR_DONE)))
		end
		nodeSetRotation(head, 0, 0, pitch)
		nodeSetRotation(neck, 0, 0, pitch * 0.35)

		-- The flame leaves the mouth along the dragon's own forward, which the whole logo has been
		-- turning;  a 3D emitter takes its direction in world axes, so it is turned here by hand.
		local aim = math.rad(pitch)
		local spin = math.rad(yaw + DRAGON_YAW)

		emitterSetDirection(breath, math.cos(aim) * math.cos(spin), math.sin(aim), -math.cos(aim) * math.sin(spin))
		if t >= BREATH_START and t < BREATH_END then
			emitterStart(breath)
			lightSetIntensity(breathLight, 26)
		else
			emitterStop(breath)
			lightSetIntensity(breathLight, 0)
		end
	end

	colorBackground(0, 0, 0, 0)
	overlayClear()
	local gone = span(t, LIFT_FROM, LIFT_TO - 0.4)

	if (tag > 0) and (gone < 1) then
		colorForeground(235, 225, 240, math.floor(255 * tag * (1 - gone)))
		fontPrint(tagX, tagY, TAGLINE)
	end

	if shotAt <= #SHOT_TIMES and t >= SHOT_TIMES[shotAt] then
		shotAt = shotAt + 1
		singeScreenshot()
	end
	if t > 8.2 then
		singeQuit()
	end

	return OVERLAY_UPDATED
end