local Timing = require("background/bg_objects/timing")
local chain_moves, frame_change, sum = Timing.chain_moves, Timing.frame_change, Timing.sum

-- BaseDancer: single dancer that starts off-screen and bounces in, then loops
local BaseDancer = {}
BaseDancer.__index = BaseDancer

function BaseDancer.new(name, index, bpm, path)
    local self = setmetatable({}, BaseDancer)
    self.name = name
    self.index = index
    self.bpm = bpm
    self.path = path or "background"
    self.is_started = false

    local tex_info = tex.get_texture_info(self.name, tostring(self.index) .. "_loop")
    local frame_count = (tex_info and tex_info.frame_count) or 1
    self.keyframes = {}
    for i = 0, frame_count - 1 do
        table.insert(self.keyframes, i)
    end

    local duration = (60000 / bpm) / 2
    local total_duration = duration * #self.keyframes
    local textures = {}
    for i, frame_idx in ipairs(self.keyframes) do
        table.insert(textures, { duration * (i - 1), duration * i, frame_idx })
    end
    self.texture_change = anim.texture_change(total_duration, textures, { loop = true })
    self.texture_change:start()

    return self
end

function BaseDancer:start()
    self.is_started = true
    local screen_scale = tex.get_screen_scale()
    local duration = 60000 / self.bpm

    self.s_bounce_up = anim.move(duration / 2, {
        start_position = math.floor(-200 * screen_scale),
        total_distance = math.floor(350 * screen_scale),
        ease_out = "quadratic",
        delay = 500
    })
    self.s_bounce_down = anim.move(duration / 2, {
        total_distance = math.floor(140 * screen_scale),
        ease_in = "quadratic",
        delay = duration / 2 + 500
    })

    local start_info = tex.get_texture_info(self.name, tostring(self.index) .. "_start")
    local s_frame_count = (start_info and start_info.frame_count) or 1
    local s_keyframes = {}
    for i = 0, s_frame_count - 1 do
        table.insert(s_keyframes, i)
    end
    local start_textures = {}
    for i, frame_idx in ipairs(s_keyframes) do
        table.insert(start_textures, { (duration / #s_keyframes) * (i - 1), (duration / #s_keyframes) * i, frame_idx })
    end
    self.s_texture_change = anim.texture_change(duration, start_textures, { delay = 500 })
    self.s_texture_change:start()
    self.s_bounce_up:start()
    self.s_bounce_down:start()
end

function BaseDancer:update(current_time_ms, bpm)
    self.texture_change:update(current_time_ms)
    if self.is_started then
        self.s_texture_change:update(current_time_ms)
        self.s_bounce_up:update(current_time_ms)
        self.s_bounce_down:update(current_time_ms)
    end
    if bpm and bpm ~= self.bpm then
        self.bpm = bpm
        local duration = (60000 / bpm) / 2
        local total_duration = duration * #self.keyframes
        local textures = {}
        for i, frame_idx in ipairs(self.keyframes) do
            table.insert(textures, { duration * (i - 1), duration * i, frame_idx })
        end
        self.texture_change = anim.texture_change(total_duration, textures, { loop = true })
        self.texture_change:start()
    end
end

function BaseDancer:draw(x)
    if not self.is_started then return end
    local y = -self.s_bounce_up.attribute + self.s_bounce_down.attribute
    if not self.s_texture_change.is_finished then
        tex.draw_texture(tex.get_texture(self.path .. "/" .. self.name .. "/" .. tostring(self.index) .. "_start"), {
            frame = self.s_texture_change.attribute, x = x, y = y
        })
    else
        tex.draw_texture(tex.get_texture(self.path .. "/" .. self.name .. "/" .. tostring(self.index) .. "_loop"), {
            frame = self.texture_change.attribute, x = x
        })
    end
end

-- Dancer0_4: dancer 4 in group 0, has a bouncing object on top
local Dancer0_4 = setmetatable({}, { __index = BaseDancer })
Dancer0_4.__index = Dancer0_4

function Dancer0_4.new(name, index, bpm, path)
    local self = setmetatable({}, Dancer0_4)
    local base = BaseDancer.new(name, index, bpm, path)
    for k, v in pairs(base) do self[k] = v end

    self.keyframes = {}
    for i = 0, 53 do
        table.insert(self.keyframes, i)
    end

    local duration = (60000 / bpm) / 2
    local total_duration = duration * #self.keyframes
    local textures = {}
    for i, frame_idx in ipairs(self.keyframes) do
        table.insert(textures, { duration * (i - 1), duration * i, frame_idx })
    end
    self.texture_change = anim.texture_change(total_duration, textures, { loop = true })
    self.texture_change:start()

    self.bounce_up = anim.move(duration, {
        total_distance = 20, ease_out = "quadratic", delay = duration * 2
    })
    self.bounce_down = anim.move(duration, {
        total_distance = 20, ease_in = "quadratic", delay = duration * 3
    })
    self.bounce_up:start()
    self.bounce_down:start()
    self._id_4_start = tex.get_texture(self.path .. "/" .. self.name .. "/" .. "4_start") or 0
    self._id_4_loop  = tex.get_texture(self.path .. "/" .. self.name .. "/" .. "4_loop") or 0
    return self
end

function Dancer0_4:update(current_time_ms, bpm)
    BaseDancer.update(self, current_time_ms, bpm)
    self.bounce_up:update(current_time_ms)
    self.bounce_down:update(current_time_ms)
    if self.bounce_down.is_finished then
        self.bounce_up:restart()
        self.bounce_down:restart()
    end
end

function Dancer0_4:draw(x)
    if not self.is_started then return end
    local sy = -self.s_bounce_up.attribute + self.s_bounce_down.attribute
    local screen_scale = tex.get_screen_scale()
    if not self.s_texture_change.is_finished then
        tex.draw_texture(self._id_4_start, {
            frame = 7, x = x, y = (-50 * screen_scale) + sy
        })
        tex.draw_texture(self._id_4_start, {
            frame = self.s_texture_change.attribute, x = x, y = sy
        })
    else
        local attr = self.texture_change.attribute
        local by = -self.bounce_up.attribute + self.bounce_down.attribute
        if attr >= 0 and attr <= 3 then
            tex.draw_texture(self._id_4_loop, { frame = 54, x = x, y = by })
        elseif attr >= 5 and attr <= 8 then
            tex.draw_texture(self._id_4_loop, { frame = 56, x = x, y = by })
        elseif attr == 4 then
            tex.draw_texture(self._id_4_loop, { frame = 55, x = x, y = by })
        end
        tex.draw_texture(self._id_4_loop, { frame = attr, x = x })
    end
end

-- DancerPoof: dancer with a poof animation on spawn
local DancerPoof = setmetatable({}, { __index = BaseDancer })
DancerPoof.__index = DancerPoof

function DancerPoof.new(name, index, bpm, path)
    local self = setmetatable({}, DancerPoof)
    local base = BaseDancer.new(name, index, bpm, path)
    for k, v in pairs(base) do self[k] = v end

    local duration = 60000 / bpm
    local poof_keyframes = {}
    for i = 0, 6 do
        table.insert(poof_keyframes, { (duration / 7) * i, (duration / 7) * (i + 1), i })
    end
    self.poof_texture_change = anim.texture_change(duration, poof_keyframes, { delay = 250 })
    self.poof_texture_change:start()
    self._id_poof = tex.get_texture(self.path .. "/" .. self.name .. "/" .. "poof") or 0
    return self
end

function DancerPoof:update(current_time_ms, bpm)
    BaseDancer.update(self, current_time_ms, bpm)
    self.poof_texture_change:update(current_time_ms)
end

function DancerPoof:draw(x)
    BaseDancer.draw(self, x)
    if not self.poof_texture_change.is_finished then
        tex.draw_texture(self._id_poof, { x = x, frame = self.poof_texture_change.attribute })
    end
end

-- DancerPoof2: like DancerPoof but uses per-index poof texture
local DancerPoof2 = setmetatable({}, { __index = DancerPoof })
DancerPoof2.__index = DancerPoof2

function DancerPoof2.new(name, index, bpm, path)
    local self = setmetatable({}, DancerPoof2)
    local base = DancerPoof.new(name, index, bpm, path)
    for k, v in pairs(base) do self[k] = v end
    return self
end

function DancerPoof2:draw(x)
    if not self.is_started then return end
    local sy = -self.s_bounce_up.attribute + self.s_bounce_down.attribute
    if not self.s_texture_change.is_finished then
        tex.draw_texture(tex.get_texture(self.path .. "/" .. self.name .. "/" .. tostring(self.index) .. "_start"), {
            frame = self.s_texture_change.attribute, x = x, y = sy
        })
    else
        tex.draw_texture(tex.get_texture(self.path .. "/" .. self.name .. "/" .. tostring(self.index) .. "_loop"), {
            frame = self.texture_change.attribute, x = x
        })
    end
    if not self.poof_texture_change.is_finished then
        tex.draw_texture(tex.get_texture(self.path .. "/" .. self.name .. "/" .. tostring(self.index) .. "_poof"), {
            x = x, frame = self.poof_texture_change.attribute
        })
    end
end

-- BaseDancerGroup: manages a pool of dancers spread across the screen
local BaseDancerGroup = {}
BaseDancerGroup.__index = BaseDancerGroup

local function get_variant_count(dancer_name)
    local keys = tex.get_texture_keys(dancer_name)
    if not keys then return 1 end
    local variants = {}
    for _, key in ipairs(keys) do
        local num = tonumber(key:match("^(%d+)"))
        if num then variants[num] = true end
    end
    local count = 0
    for _ in pairs(variants) do count = count + 1 end
    return math.max(1, count)
end

function BaseDancerGroup.new(index, bpm, max_dancers, path, dancer_class)
    local self = setmetatable({}, BaseDancerGroup)
    dancer_class = dancer_class or BaseDancer
    self.name = "dancer_" .. index
    self.active_count = 0
    self.path = path or "background"
    tex.load_folder(self.path, "dancer/" .. self.name)
    -- center(2), left(1), right(3), far-left(0), far-right(4) — 0-indexed
    self.spawn_positions = { 2, 1, 3, 0, 4 }
    self.active_dancers = {}
    self.max_dancers = max_dancers

    local variant_count = get_variant_count(self.name)
    self.dancers = {}
    for i = 1, max_dancers do
        local variant_idx = (i - 1) % variant_count
        local dancer = dancer_class.new(self.name, variant_idx, bpm, self.path)
        dancer.group = self
        table.insert(self.dancers, dancer)
    end

    -- Shuffle dancers
    for i = #self.dancers, 2, -1 do
        local j = math.random(1, i)
        self.dancers[i], self.dancers[j] = self.dancers[j], self.dancers[i]
    end

    self.needs_initial_dancer = true
    return self
end

function BaseDancerGroup:add_dancer()
    if self.active_count < #self.dancers and self.active_count < #self.spawn_positions then
        self.active_count = self.active_count + 1
        local position = self.spawn_positions[self.active_count] + 1 -- convert to 1-indexed
        local dancer = self.dancers[self.active_count]
        self.active_dancers[position] = dancer
        dancer:start()
    end
end

function BaseDancerGroup:remove_dancer()
    if self.active_count > 1 then
        local position = self.spawn_positions[self.active_count] + 1
        self.active_dancers[position] = nil
        self.active_count = self.active_count - 1
    end
end

function BaseDancerGroup:update(current_time_ms, bpm)
    if self.needs_initial_dancer then
        self.needs_initial_dancer = false
        self:add_dancer()
    end
    for _, dancer in ipairs(self.dancers) do
        dancer:update(current_time_ms, bpm)
    end
end

function BaseDancerGroup:draw()
    local screen_width = tex.get_screen_width()
    local num_dancers = self.max_dancers

    local first_dancer = nil
    for i = 1, num_dancers do
        local d = self.active_dancers[i]
        if d then
            first_dancer = d; break
        end
    end
    if not first_dancer then return end

    local info = tex.get_texture_info(self.name, tostring(first_dancer.index) .. "_loop")
    local dancer_width = info and info.width or 0

    local available_space = screen_width - (num_dancers * dancer_width)
    local spacing = available_space / (num_dancers + 1)

    for i = 1, num_dancers do
        local dancer = self.active_dancers[i]
        if dancer then
            local x_pos = math.floor(spacing + (i - 1) * (dancer_width + spacing))
            dancer:draw(x_pos)
        end
    end
end

-- Draws dancers on fixed slot centres (Lumen positions) instead of even spacing
function BaseDancerGroup:draw_slots(centers, order)
    local screen_scale = tex.get_screen_scale()
    for _, i in ipairs(order) do
        local dancer = self.active_dancers[i]
        if dancer then
            local info = tex.get_texture_info(self.name, tostring(dancer.index) .. "_loop")
            dancer:draw(math.floor(centers[i] * screen_scale - info.width / 2))
        end
    end
end

-- Beats since the first dancer started dancing: the routine's shared clock, so dancers that
-- join later dance in step with the rest. Re-anchored when the bpm changes so it doesn't jump.
function BaseDancerGroup:dance_clock(now, beat)
    local c = self.clock
    if not c then
        c = { t0 = now, beat = beat }
        self.clock = c
    elseif c.beat ~= beat then
        c.t0, c.beat = now - (now - c.t0) / c.beat * beat, beat
    end
    return (now - c.t0) / beat
end

-- Like remove_dancer, but the dancer stays in its slot to play its exit
function BaseDancerGroup:leave_dancer()
    if self.active_count > 1 then
        self.active_dancers[self.spawn_positions[self.active_count] + 1]:leave()
        self.active_count = self.active_count - 1
    end
end

function BaseDancerGroup:destroy()
    tex.unload_folder(self.path, "dancer/" .. self.name)
end

-- DancerGroup0: index 0 uses BaseDancers 0-3 + Dancer0_4 at position 4
local DancerGroup0 = setmetatable({}, { __index = BaseDancerGroup })
DancerGroup0.__index = DancerGroup0

function DancerGroup0.new(index, bpm, max_dancers, path)
    local self = setmetatable({}, DancerGroup0)
    self.name = "dancer_" .. index
    self.active_count = 0
    self.path = path or "background"
    tex.load_folder(self.path, "dancer/" .. self.name)
    self.spawn_positions = { 2, 1, 3, 0, 4 }
    self.active_dancers = {}
    self.max_dancers = max_dancers
    self.dancers = {
        BaseDancer.new(self.name, 0, bpm, self.path),
        BaseDancer.new(self.name, 1, bpm, self.path),
        BaseDancer.new(self.name, 2, bpm, self.path),
        BaseDancer.new(self.name, 3, bpm, self.path),
        Dancer0_4.new(self.name, 4, bpm, self.path)
    }
    for i = #self.dancers, 2, -1 do
        local j = math.random(1, i)
        self.dancers[i], self.dancers[j] = self.dancers[j], self.dancers[i]
    end
    self.needs_initial_dancer = true
    return self
end

-- DancerGroupPoof1: uses DancerPoof
local DancerGroupPoof1 = setmetatable({}, { __index = BaseDancerGroup })
DancerGroupPoof1.__index = DancerGroupPoof1

function DancerGroupPoof1.new(index, bpm, max_dancers, path)
    return BaseDancerGroup.new(index, bpm, max_dancers, path, DancerPoof)
end

-- DancerGroupPoof2: uses DancerPoof2
local DancerGroupPoof2 = setmetatable({}, { __index = BaseDancerGroup })
DancerGroupPoof2.__index = DancerGroupPoof2

function DancerGroupPoof2.new(index, bpm, max_dancers, path)
    return BaseDancerGroup.new(index, bpm, max_dancers, path, DancerPoof2)
end

-- LumenDancer: a dancer ported from Lumen data, driven by a spec of beat timings:
--   start_offset, in_moves, squash, in_frames: entry from below (chain_moves / frame_change)
--   dance: looping frame_change steps, kept in step across the group (see dance_clock);
--   out_moves, out_squash, out_frame: exit (optional);
--   out_frames: frame_change steps for the exit instead of the single out_frame
-- Dancer.lumen(specs) makes a class for BaseDancerGroup; specs[index] or specs.default.
local LumenDancer = {}
LumenDancer.__index = LumenDancer

function LumenDancer.new(cls, name, index, bpm, path)
    local self   = setmetatable({}, cls)
    self.name    = name
    self.index   = index
    self.spec    = cls.specs[index] or cls.specs.default
    self._id     = tex.get_texture(path .. "/" .. name .. "/" .. index .. "_loop") or 0
    self.state   = nil -- nil (hidden), "in", "dance", "out"
    self.moves   = {}
    self.squash  = {}
    self.bpm     = bpm
    self.beat    = 60000 / bpm
    return self
end

-- The routine's steps from `pos` beats in to the end of the cycle
local function rest_of(steps, pos)
    local out, t = {}, 0
    for _, step in ipairs(steps) do
        local finish = t + step[2]
        if finish > pos then table.insert(out, { step[1], finish - math.max(t, pos) }) end
        t = finish
    end
    return out
end

function LumenDancer:set_bpm(bpm, current_time_ms)
    self.bpm  = bpm
    self.beat = 60000 / bpm
    if self.state == "dance" then self:start_dance(current_time_ms) end
end

-- Starts the routine at the point the rest of the group is at: plays the rest of the current
-- cycle, then loops it from the top
function LumenDancer:start_dance(current_time_ms)
    local steps, period = self.spec.dance, 0
    for _, step in ipairs(steps) do period = period + step[2] end
    local pos = self.group and self.group:dance_clock(current_time_ms, self.beat) % period or 0
    local lead = rest_of(steps, pos)
    self.dance_lead = #lead > 0 and pos > 0 and frame_change(lead, self.beat) or nil
    self.dance = frame_change(steps, self.beat, { loop = true })
    if self.dance_lead then self.dance_lead:start() else self.dance:start() end
end

function LumenDancer:start()
    local scale     = tex.get_screen_scale()
    self.state      = "in"
    self.offset     = math.floor(self.spec.start_offset * scale)
    self.moves      = chain_moves(self.spec.in_moves, self.beat, scale)
    self.squash     = chain_moves(self.spec.squash, self.beat, scale)
    self.in_frames  = frame_change(self.spec.in_frames, self.beat)
    self.in_frames:start()
end

function LumenDancer:leave()
    if not self.spec.out_moves then
        self.state = nil
        return
    end
    local scale = tex.get_screen_scale()
    self.offset = self.offset + sum(self.moves) -- leaves from wherever it is
    self.state  = "out"
    self.moves  = chain_moves(self.spec.out_moves, self.beat, scale)
    self.squash = chain_moves(self.spec.out_squash or {}, self.beat, scale)
    if self.spec.out_frames then
        self.out_frames = frame_change(self.spec.out_frames, self.beat)
        self.out_frames:start()
    end
end

function LumenDancer:update(current_time_ms, bpm)
    if bpm and bpm ~= self.bpm then self:set_bpm(bpm, current_time_ms) end
    if not self.state then return end
    for _, m in ipairs(self.moves) do m:update(current_time_ms) end
    for _, m in ipairs(self.squash) do m:update(current_time_ms) end
    if self.state == "in" then
        self.in_frames:update(current_time_ms)
        if self.in_frames.is_finished then
            self.state = "dance"
            self:start_dance(current_time_ms)
        end
    elseif self.state == "out" and self.moves[#self.moves].is_finished then
        self.state = nil
    end
    if self.state == "dance" then
        if self.dance_lead then
            self.dance_lead:update(current_time_ms)
            if self.dance_lead.is_finished then
                self.dance_lead = nil
                self.dance:start()
            end
        end
        self.dance:update(current_time_ms)
    end
    if self.state == "out" and self.out_frames then self.out_frames:update(current_time_ms) end
end

function LumenDancer:draw(x)
    if not self.state then return end
    local frame
    if self.state == "in" then
        frame = self.in_frames.attribute
    elseif self.state == "out" then
        frame = self.out_frames and self.out_frames.attribute or self.spec.out_frame
    else
        frame = (self.dance_lead or self.dance).attribute
    end
    -- squash keeps the feet planted: shrink the height and push the top down
    local squash = sum(self.squash)
    tex.draw_texture(self._id, {
        frame = frame,
        x = x,
        y = self.offset + sum(self.moves) + squash,
        y2 = -squash,
    })
end

local function lumen(specs)
    local cls = setmetatable({ specs = specs }, { __index = LumenDancer })
    cls.__index = cls
    cls.new = function(...) return LumenDancer.new(cls, ...) end
    return cls
end

-- Factory: maps dancer index 0-20 to the appropriate group class
local Dancer = {}
Dancer.Base = BaseDancer
Dancer.BaseDancerGroup = BaseDancerGroup
Dancer.lumen = lumen

function Dancer.create(index, bpm, path, max_dancers)
    max_dancers = max_dancers or 5
    local map = {
        DancerGroup0, DancerGroup0, DancerGroup0,
        BaseDancerGroup, BaseDancerGroup, BaseDancerGroup,
        BaseDancerGroup,
        DancerGroupPoof1, DancerGroupPoof1,
        BaseDancerGroup, BaseDancerGroup, BaseDancerGroup,
        DancerGroupPoof2, DancerGroupPoof2,
        BaseDancerGroup, BaseDancerGroup,
        DancerGroupPoof2,
        BaseDancerGroup, BaseDancerGroup, BaseDancerGroup, BaseDancerGroup
    }
    local cls = map[index + 1]
    return cls.new(index, bpm, max_dancers, path)
end

return Dancer