local DonBGBase       = require("background/bg_objects/donbg/base")
local DonBG           = require("background/bg_objects/donbg")
local Fever           = require("background/bg_objects/fever")
local Dancer          = require("background/bg_objects/dancer")
local RendaController = require("background/bg_objects/renda")
local ChibiController = require("background/bg_objects/chibi")
local BaseChibi       = require("background/bg_objects/chibi/base")
local Timing          = require("background/bg_objects/timing")

local COLLAB_PATH     = "background/collab/ia"
local MAX_DANCERS     = 5

local chain_moves, sum = Timing.chain_moves, Timing.sum

-- No footer: the stage in bg_normal reaches the bottom of the screen.

-- Normal background: the stage, with confetti falling in front of five spotlights. The
-- confetti is a 20-frame loop at 30 fps (ambient, in ms), the same frame on every copy.
local CONFETTI_COPIES = 5
local CONFETTI_FPS    = 30

local IaBGNormal   = {}
IaBGNormal.__index = IaBGNormal

function IaBGNormal.new()
    local self = setmetatable({}, IaBGNormal)
    self.name = "bg_0"
    tex.load_folder(COLLAB_PATH, "bg_normal/" .. self.name)
    local function id(key) return tex.get_texture(COLLAB_PATH .. "/" .. self.name .. "/" .. key) or 0 end
    self._id_bg       = id("background")
    self._id_confetti = id("confetti")
    self._id_lights   = id("lights")
    self.frames       = tex.get_texture_info(self.name, "confetti").frame_count
    self.frame        = 0
    return self
end

function IaBGNormal:update(current_time_ms)
    self.frame = math.floor(current_time_ms * CONFETTI_FPS / 1000) % self.frames
end

function IaBGNormal:draw()
    tex.draw_texture(self._id_bg)
    for i = 0, CONFETTI_COPIES - 1 do
        tex.draw_texture(self._id_confetti, { index = i, frame = self.frame, blend = "additive" })
    end
    tex.draw_texture(self._id_lights)
end

function IaBGNormal:destroy() tex.unload_folder(COLLAB_PATH, "bg_normal/" .. self.name) end

-- Clear background: a bubble backdrop drops in over the stage and bounces, scrolling left
-- 320px every 2 beats (it repeats every 320px). A beat later, spotlights fade in and flash
-- in three pairs every 1.5 beats, and two sparkle layers pulse in turn. Losing clear slides
-- the backdrop down off the screen while the lights fade. Timed in beats; drawn over
-- bg_normal, which shows through before and after.
local BG_FEVER_DROP   = { { 1, 360, "in" }, { 0.45, -50, "out" }, { 0.3, 50, "in" } } -- from 360 above
local BG_FEVER_EXIT   = 1     -- beats to slide 400px down
local BG_FEVER_SCROLL = 160   -- px a beat
local BG_FEVER_TILE   = 640
local LIGHTS_DELAY    = 1     -- beats after the drop starts
local SPOTS_FADE_IN   = 0.75
local LIGHTS_FADE_OUT = 0.35
-- each pair: { texture.json index 0 key, index 1 key (mirrored), beat in the 1.5-beat cycle }
local SPOT_CYCLE      = 1.5
local SPOT_PAIRS      = {
    { "spot_pink", "spot_pink", 0 },
    { "spot_green", "spot_cyan", 0.5 },
    { "spot_cyan", "spot_green", 1 },
}
local SPARKLE_CYCLE = 2

-- a spotlight flash: quick fade in, hold, fade out over half a beat
local function flash(u)
    if u < 0.125 then return u / 0.125 end
    if u < 0.5 then return 1 end
    if u < 1 then return (1 - u) / 0.5 end
    return 0
end

-- a sparkle pulse over 2 beats: dark, fade in to the beat, fade out, dark
local function pulse(u)
    if u < 0.25 or u >= 1.75 then return 0 end
    if u < 1 then return (u - 0.25) / 0.75 end
    return (1.75 - u) / 0.75
end

local IaBGFever   = {}
IaBGFever.__index = IaBGFever

function IaBGFever.new(bpm)
    local self = setmetatable({}, IaBGFever)
    self.name = "bg_fever_0"
    tex.load_folder(COLLAB_PATH, "bg_fever/" .. self.name)
    local function id(key) return tex.get_texture(COLLAB_PATH .. "/" .. self.name .. "/" .. key) or 0 end
    self._id_bg      = id("background")
    self._id_sparkle = id("sparkle")
    self._id_spot    = { spot_cyan = id("spot_cyan"), spot_pink = id("spot_pink"), spot_green = id("spot_green") }
    self.beat        = 60000 / bpm
    self.scale       = tex.get_screen_scale()
    self.state       = nil -- nil (hidden), "in", "out"
    return self
end

function IaBGFever:y() return self.y0 + sum(self.drop) end

function IaBGFever:lights(moves, offset) return (offset + sum(moves)) / 1000 end

function IaBGFever:start()
    self.state   = "in"
    self.t       = 0 -- beats since the drop started: the scroll and light cycles
    self.y0      = math.floor(-360 * self.scale)
    self.drop    = chain_moves(BG_FEVER_DROP, self.beat, self.scale)
    self.spots   = chain_moves({ { LIGHTS_DELAY, 0 }, { SPOTS_FADE_IN, 1000 } }, self.beat, 1)
    self.sparkle = chain_moves({ { LIGHTS_DELAY, 0 }, { 0, 1000 } }, self.beat, 1)
    self.spots0, self.sparkle0 = 0, 0
end

-- slides down and fades the lights from wherever they are
function IaBGFever:stop()
    if self.state ~= "in" then return end
    local y, spots, sparkle = self:y(), self:lights(self.spots, self.spots0), self:lights(self.sparkle, self.sparkle0)
    self.state   = "out"
    self.y0      = y
    self.drop    = chain_moves({ { BG_FEVER_EXIT, 400 - y / self.scale } }, self.beat, self.scale)
    self.spots0, self.sparkle0 = math.floor(spots * 1000), math.floor(sparkle * 1000)
    self.spots   = chain_moves({ { LIGHTS_FADE_OUT, -self.spots0 } }, self.beat, 1)
    self.sparkle = chain_moves({ { LIGHTS_FADE_OUT, -self.sparkle0 } }, self.beat, 1)
end

local function update_all(moves, current_time_ms)
    for _, m in ipairs(moves) do m:update(current_time_ms) end
end

function IaBGFever:update(current_time_ms, bpm)
    if bpm then self.beat = 60000 / bpm end
    local dt = current_time_ms - (self.last_ms or current_time_ms)
    self.last_ms = current_time_ms
    if not self.state then return end
    self.t = self.t + dt / self.beat
    update_all(self.drop, current_time_ms)
    update_all(self.spots, current_time_ms)
    update_all(self.sparkle, current_time_ms)
    if self.state == "out" and self.drop[#self.drop].is_finished then self.state = nil end
end

function IaBGFever:draw()
    if not self.state then return end
    local y = self:y()
    local tile = BG_FEVER_TILE * self.scale
    local x = (-160 - (self.t * BG_FEVER_SCROLL) % 320) * self.scale
    while x < tex.get_screen_width() do
        tex.draw_texture(self._id_bg, { x = x, y = y })
        x = x + tile
    end

    local t = self.t - LIGHTS_DELAY
    if t < 0 then return end
    local spots = self:lights(self.spots, self.spots0)
    for _, pair in ipairs(SPOT_PAIRS) do
        local fade = spots * flash((t - pair[3]) % SPOT_CYCLE)
        if fade > 0 then
            tex.draw_texture(self._id_spot[pair[1]], { index = 0, fade = fade })
            tex.draw_texture(self._id_spot[pair[2]], { index = 1, fade = fade, mirror = "horizontal" })
        end
    end
    local sparkle = self:lights(self.sparkle, self.sparkle0)
    for frame = 0, 1 do -- the second layer pulses a beat later
        local fade = sparkle * pulse((t + frame) % SPARKLE_CYCLE)
        for i = 0, 1 do tex.draw_texture(self._id_sparkle, { index = i, frame = frame, fade = fade }) end
    end
end

function IaBGFever:destroy() tex.unload_folder(COLLAB_PATH, "bg_fever/" .. self.name) end

-- Fever line-up: the yokai crowd (left, right) with additive glow sticks over them, two poses
local FEVER_SPEC = {
    rise = 270, peak = 70, bounce = 70, drop = 340, poses = true,
    keys = { "overlay_l", "overlay_r", "glow_l", "glow_r" },
    additive = { glow_l = true, glow_r = true },
}

-- Dancers
-- Timed in beats. Each jumps up from below, lands with a squash, then loops a 32-beat
-- routine; the small ones hop off when removed. Poses pivot about the feet (bottom-left).

-- a pose with an accent: stretches (sy) or narrows (sx) over a quarter beat and settles back
local function accent(frame, beats, s)
    return {
        { frame, 0.25, to = { nil, nil, "out", sx = s.sx, sy = s.sy } },
        { frame, 0.25, sx = s.sx, sy = s.sy, to = { nil, nil, "in", sx = 1, sy = 1 } },
        { frame, beats - 0.5 },
    }
end

local SWAY = { { 1, 1, x = 0, y = 0 }, { 0, 1 }, { 2, 1 }, { 0, 1 } }
local STRETCH, NARROW = { sy = 1.04 }, { sx = 0.96 }

local SMALL_DANCER = {
    origin = { 0, 184 },
    enter  = {
        beats = 2,
        { 0,     0, 0, 358 },
        { 0.35,  0, 0, 358, to = { 0, -38, "out" } },               -- jumps up from below
        { 0.95,  0, 0, -38, to = { 0, 0, "in" } },
        { 1.2,   0, 0, 0, to = { nil, nil, "out", sy = 0.96 } },    -- lands with a squash
        { 1.325, 0, 0, 0, sy = 0.96, to = { nil, nil, "in", sy = 1 } },
        { 1.45,  0, 0, 0 },
    },
    dance  = Timing.steps(SWAY, SWAY, SWAY, SWAY,
        { { 3, 2 } }, accent(4, 2, STRETCH), { { 3, 2 } }, accent(5, 2, STRETCH),
        { { 6, 0.5 }, { 7, 0.5 }, { 8, 0.5 }, { 9, 0.5 } },
        accent(10, 2, NARROW), accent(11, 3, STRETCH), { { 0, 1 } }),
    leave  = {
        beats = 1.35, key = "loop",
        { 0,     12, 0, 0, to = { nil, nil, "out", sy = 0.96 } },   -- crouches
        { 0.15,  12, 0, 0, sy = 0.96, to = { nil, nil, "in", sy = 1 } },
        { 0.275, 12, 0, -13, to = { 0, -62, "out" } },              -- hops up and drops away
        { 0.5,   12, 0, -62, to = { 0, 358, "in" } },
    },
}

-- IA in the centre: jumps in on her entry frame and lands on her standing pose; never leaves
local IA_SWAY = { { 1, 1, x = 0, y = 0 }, { 2, 1 }, { 3, 1 }, { 2, 1 } }
local IA_DANCER = {
    origin = { 0, 328 },
    enter  = {
        beats = 2,
        { 0,     0, 0, 357 },
        { 0.35,  0, 0, 357, to = { 0, -38, "out" } },
        { 0.95,  0, 0, -38, to = { 0, -7, "in" } },
        { 1.175, 1, 0, 0, to = { nil, nil, "out", sy = 0.96 } },
        { 1.325, 1, 0, 0, sy = 0.96, to = { nil, nil, "in", sy = 1 } },
        { 1.45,  1, 0, 0 },
    },
    dance  = Timing.steps(IA_SWAY, IA_SWAY, IA_SWAY, IA_SWAY,
        { { 4, 2 } }, accent(0, 2, { sy = 1.02 }), { { 4, 2 } }, accent(5, 2, { sy = 1.02 }),
        { { 6, 0.5 }, { 7, 0.5 }, { 8, 0.5 }, { 9, 0.5 }, { 10, 0.5 },
          { 11, 0.5 }, { 12, 0.5 }, { 13, 0.5 }, { 14, 0.5 }, { 15, 0.5 }, { 16, 2 }, { 2, 1 } }),
}

local IA_INDEX   = 4
local IA_DANCERS = Dancer.define({ default = SMALL_DANCER, [IA_INDEX] = IA_DANCER })

-- Fixed slots (far-left .. far-right), from Lumen's dancer positions
local DANCER_CENTERS    = { 183, 417, 640, 863, 1097 }
local DANCER_DRAW_ORDER = { 5, 1, 4, 2, 3 } -- outer pairs first, IA on top
-- dancer index by join order: joins fill the centre, left, right, far-left, far-right slots
local DANCER_JOIN_ORDER = { IA_INDEX, 3, 2, 1, 0 }

-- Chibi IA for good hits: hops in growing from 70% size, then floats across the don band,
-- bobbing through three poses every 2 beats
local IA_CHIBI = {
    key    = "1",
    period = 2,
    poses  = {
        { 0,     0, 0, -12, to = { 0, 1 } },
        { 0.4,   1, 0, 0, to = { 0, 6 } },
        { 0.75,  2, 8, 4, to = { 8, 6 } },
        { 0.875, 2, 8, 5, to = { 8, -14 } },
        { 1.35,  1, 8, -14, to = { 8, -17 } },
        { 1.475, 1, 8, -17, to = { 8, -12 } },
    },
}

-- Don band: miku/GUMI's parallax band; the base tiles from x 148
local function donbg_spec()
    local spec = DonBG.parallax(-164)
    spec.layers[1].x = 148
    return spec
end

-- Background

local IaBackground = {}
IaBackground.__index = IaBackground

function IaBackground.new(player_num, bpm)
    local self          = setmetatable({}, IaBackground)
    self.donbg          = DonBGBase.new(1, player_num, COLLAB_PATH, donbg_spec())
    self.bg_normal      = IaBGNormal.new()
    self.bg_fever       = IaBGFever.new(bpm)
    self.fever          = Fever.new(bpm, COLLAB_PATH, FEVER_SPEC)
    self.dancer         = Dancer.BaseDancerGroup.new(0, bpm, MAX_DANCERS, COLLAB_PATH, IA_DANCERS)
    local by_index = {}
    for _, d in ipairs(self.dancer.dancers) do by_index[d.index] = d end
    for i, index in ipairs(DANCER_JOIN_ORDER) do self.dancer.dancers[i] = by_index[index] end
    self.renda          = RendaController.new(COLLAB_PATH, 0, RendaController.ACROSS)
    self.chibi          = ChibiController.new(bpm, COLLAB_PATH, 1)
    self.is_clear       = false
    self.is_rainbow     = false
    self.last_milestone = 1
    return self
end

function IaBackground:update(current_ms, bpm)
    self.donbg:update(current_ms, bpm)
    self.bg_normal:update(current_ms)
    self.bg_fever:update(current_ms, bpm)
    self.fever:update(current_ms, bpm)
    self.dancer:update(current_ms, bpm)
    self.renda:update(current_ms)
    self.chibi:update(current_ms, bpm)
end

function IaBackground:handle_good(player_num) BaseChibi.add(self.chibi, IA_CHIBI, COLLAB_PATH, player_num) end

function IaBackground:handle_ok(player_num) BaseChibi.add(self.chibi, IA_CHIBI, COLLAB_PATH, player_num) end

function IaBackground:handle_bad(player_num) self.chibi:add_chibi(player_num, true) end

function IaBackground:handle_drumroll(player_num) self.renda:add_renda() end

function IaBackground:handle_balloon(player_num) self.renda:add_renda() end

function IaBackground:handle_gauge(player_num, progress, is_clear, is_rainbow)
    self.donbg:set_clear(is_clear)
    if is_clear and not self.is_clear then self.bg_fever:start() end
    if not is_clear and self.is_clear then self.bg_fever:stop() end
    if is_rainbow and not self.is_rainbow then self.fever:start() end
    if not is_rainbow and self.is_rainbow then self.fever:stop() end
    self.is_clear   = is_clear
    self.is_rainbow = is_rainbow

    local current_milestone
    if is_clear then
        current_milestone = MAX_DANCERS
    else
        current_milestone = math.min(MAX_DANCERS - 1, math.floor(progress * MAX_DANCERS))
    end
    if current_milestone > self.last_milestone then
        for _ = 1, current_milestone - self.last_milestone do self.dancer:add_dancer() end
        self.last_milestone = current_milestone
    elseif current_milestone < self.last_milestone then
        for _ = 1, self.last_milestone - current_milestone do self.dancer:leave_dancer() end
        self.last_milestone = current_milestone
    end
end

function IaBackground:draw_back()
    self.bg_normal:draw()
    self.bg_fever:draw()
    self.donbg:draw()
    self.renda:draw()
    self.dancer:draw_slots(DANCER_CENTERS, DANCER_DRAW_ORDER)
    self.fever:draw()
    self.chibi:draw()
end

function IaBackground:draw_fore() end

function IaBackground:destroy()
    self.donbg:destroy()
    self.bg_normal:destroy()
    self.bg_fever:destroy()
    self.fever:destroy()
    self.dancer:destroy()
    self.renda:destroy()
    self.chibi:destroy()
end

return IaBackground