--[[
Lua implementation of HSLuv and HPLuv color spaces
Homepage: http://www.hsluv.org/

Copyright (C) 2019 Alexei Boronine

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
associated documentation files (the "Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the
following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial
portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
]]

local hsluv = {}

local hexChars = "0123456789abcdef"

local distance_line_from_origin = function(line)
    return math.abs(line.intercept) / math.sqrt((line.slope ^ 2) + 1)
end

local length_of_ray_until_intersect = function(theta, line)
    return line.intercept / (math.sin(theta) - line.slope * math.cos(theta))
end

hsluv.get_bounds = function(l)
    local result = {}
    local sub2
    local sub1 = ((l + 16) ^ 3) / 1560896
    if sub1 > hsluv.epsilon then
        sub2 = sub1
    else
        sub2 = l / hsluv.kappa
    end

    for i = 1, 3 do
        local m1 = hsluv.m[i][1]
        local m2 = hsluv.m[i][2]
        local m3 = hsluv.m[i][3]

        for t = 0, 1 do
            local top1 = (284517 * m1 - 94839 * m3) * sub2
            local top2 = (838422 * m3 + 769860 * m2 + 731718 * m1) * l * sub2 - 769860 * t * l
            local bottom = (632260 * m3 - 126452 * m2) * sub2 + 126452 * t
            table.insert(result, {
                slope = top1 / bottom,
                intercept = top2 / bottom,
            })
        end
    end
    return result
end

hsluv.max_safe_chroma_for_l = function(l)
    local bounds = hsluv.get_bounds(l)
    local min = 1.7976931348623157e+308

    for i = 1, 6 do
        local length = distance_line_from_origin(bounds[i])
        if length >= 0 then
            min = math.min(min, length)
        end
    end
    return min
end

hsluv.max_safe_chroma_for_lh = function(l, h)
    local hrad = h / 360 * math.pi * 2
    local bounds = hsluv.get_bounds(l)
    local min = 1.7976931348623157e+308

    for i = 1, 6 do
        local bound = bounds[i]
        local length = length_of_ray_until_intersect(hrad, bound)
        if length >= 0 then
            min = math.min(min, length)
        end
    end
    return min
end

hsluv.dot_product = function(a, b)
    local sum = 0
    for i = 1, 3 do
        sum = sum + a[i] * b[i]
    end
    return sum
end

hsluv.from_linear = function(c)
    if c <= 0.0031308 then
        return 12.92 * c
    else
        return 1.055 * (c ^ 0.416666666666666685) - 0.055
    end
end

hsluv.to_linear = function(c)
    if c > 0.04045 then
        return ((c + 0.055) / 1.055) ^ 2.4
    else
        return c / 12.92
    end
end

hsluv.xyz_to_rgb = function(tuple)
    return {
        hsluv.from_linear(hsluv.dot_product(hsluv.m[1], tuple)),
        hsluv.from_linear(hsluv.dot_product(hsluv.m[2], tuple)),
        hsluv.from_linear(hsluv.dot_product(hsluv.m[3], tuple)),
    }
end

hsluv.rgb_to_xyz = function(tuple)
    local rgbl = {
        hsluv.to_linear(tuple[1]),
        hsluv.to_linear(tuple[2]),
        hsluv.to_linear(tuple[3]),
    }
    return {
        hsluv.dot_product(hsluv.minv[1], rgbl),
        hsluv.dot_product(hsluv.minv[2], rgbl),
        hsluv.dot_product(hsluv.minv[3], rgbl),
    }
end

hsluv.y_to_l = function(Y)
    if Y <= hsluv.epsilon then
        return Y / hsluv.refY * hsluv.kappa
    else
        return 116 * ((Y / hsluv.refY) ^ 0.333333333333333315) - 16
    end
end

hsluv.l_to_y = function(L)
    if L <= 8 then
        return hsluv.refY * L / hsluv.kappa
    else
        return hsluv.refY * (((L + 16) / 116) ^ 3)
    end
end

hsluv.xyz_to_luv = function(tuple)
    local X = tuple[1]
    local Y = tuple[2]
    local divider = X + 15 * Y + 3 * tuple[3]
    local varU = 4 * X
    local varV = 9 * Y
    if divider ~= 0 then
        varU = varU / divider
        varV = varV / divider
    else
        varU = 0
        varV = 0
    end
    local L = hsluv.y_to_l(Y)
    if L == 0 then
        return { 0, 0, 0 }
    end
    return { L, 13 * L * (varU - hsluv.refU), 13 * L * (varV - hsluv.refV) }
end

hsluv.luv_to_xyz = function(tuple)
    local L = tuple[1]
    local U = tuple[2]
    local V = tuple[3]
    if L == 0 then
        return { 0, 0, 0 }
    end
    local varU = U / (13 * L) + hsluv.refU
    local varV = V / (13 * L) + hsluv.refV
    local Y = hsluv.l_to_y(L)
    local X = 0 - (9 * Y * varU) / (((varU - 4) * varV) - varU * varV)
    return { X, Y, (9 * Y - 15 * varV * Y - varV * X) / (3 * varV) }
end

hsluv.luv_to_lch = function(tuple)
    local L = tuple[1]
    local U = tuple[2]
    local V = tuple[3]
    local C = math.sqrt(U * U + V * V)
    local H
    if C < 0.00000001 then
        H = 0
    else
        H = math.atan2(V, U) * 180.0 / 3.1415926535897932
        if H < 0 then
            H = 360 + H
        end
    end
    return { L, C, H }
end

hsluv.lch_to_luv = function(tuple)
    local L = tuple[1]
    local C = tuple[2]
    local Hrad = tuple[3] / 360.0 * 2 * math.pi
    return { L, math.cos(Hrad) * C, math.sin(Hrad) * C }
end

hsluv.hsluv_to_lch = function(tuple)
    local H = tuple[1]
    local S = tuple[2]
    local L = tuple[3]
    if L > 99.9999999 then
        return { 100, 0, H }
    end
    if L < 0.00000001 then
        return { 0, 0, H }
    end
    return { L, hsluv.max_safe_chroma_for_lh(L, H) / 100 * S, H }
end

hsluv.lch_to_hsluv = function(tuple)
    local L = tuple[1]
    local C = tuple[2]
    local H = tuple[3]
    local max_chroma = hsluv.max_safe_chroma_for_lh(L, H)
    if L > 99.9999999 then
        return { H, 0, 100 }
    end
    if L < 0.00000001 then
        return { H, 0, 0 }
    end

    return { H, C / max_chroma * 100, L }
end

hsluv.hpluv_to_lch = function(tuple)
    local H = tuple[1]
    local S = tuple[2]
    local L = tuple[3]
    if L > 99.9999999 then
        return { 100, 0, H }
    end
    if L < 0.00000001 then
        return { 0, 0, H }
    end
    return { L, hsluv.max_safe_chroma_for_l(L) / 100 * S, H }
end

hsluv.lch_to_hpluv = function(tuple)
    local L = tuple[1]
    local C = tuple[2]
    local H = tuple[3]
    if L > 99.9999999 then
        return { H, 0, 100 }
    end
    if L < 0.00000001 then
        return { H, 0, 0 }
    end
    return { H, C / hsluv.max_safe_chroma_for_l(L) * 100, L }
end

hsluv.rgb_to_hex =

hsluv.hex_to_rgb = function(hex)
    hex = string.lower(hex)
    local ret = {}
    for i = 0, 2 do
        local char1 = string.sub(hex, i * 2 + 2, i * 2 + 2)
        local char2 = string.sub(hex, i * 2 + 3, i * 2 + 3)
        local digit1 = string.find(hexChars, char1) - 1
        local digit2 = string.find(hexChars, char2) - 1
        ret[i + 1] = (digit1 * 16 + digit2) / 255.0
    end
    return ret
end

hsluv.lch_to_rgb = function(tuple)
    return hsluv.xyz_to_rgb(hsluv.luv_to_xyz(hsluv.lch_to_luv(tuple)))
end

hsluv.rgb_to_lch = function(tuple)
    return hsluv.luv_to_lch(hsluv.xyz_to_luv(hsluv.rgb_to_xyz(tuple)))
end

hsluv.hsluv_to_rgb = function(tuple)
    return hsluv.lch_to_rgb(hsluv.hsluv_to_lch(tuple))
end

hsluv.rgb_to_hsluv = function(tuple)
    return hsluv.lch_to_hsluv(hsluv.rgb_to_lch(tuple))
end

hsluv.hpluv_to_rgb = function(tuple)
    return hsluv.lch_to_rgb(hsluv.hpluv_to_lch(tuple))
end

hsluv.rgb_to_hpluv = function(tuple)
    return hsluv.lch_to_hpluv(hsluv.rgb_to_lch(tuple))
end

hsluv.hsluv_to_hex = function(tuple)
    return hsluv.rgb_to_hex(hsluv.hsluv_to_rgb(tuple))
end

hsluv.hpluv_to_hex = function(tuple)
    return hsluv.rgb_to_hex(hsluv.hpluv_to_rgb(tuple))
end

hsluv.hex_to_hsluv = function(s)
    return hsluv.rgb_to_hsluv(hsluv.hex_to_rgb(s))
end

hsluv.hex_to_hpluv = function(s)
    return hsluv.rgb_to_hpluv(hsluv.hex_to_rgb(s))
end

hsluv.m = {
    { 3.240969941904521, -1.537383177570093, -0.498610760293 },
    { -0.96924363628087, 1.87596750150772, 0.041555057407175 },
    { 0.055630079696993, -0.20397695888897, 1.056971514242878 },
}
hsluv.minv = {
    { 0.41239079926595, 0.35758433938387, 0.18048078840183 },
    { 0.21263900587151, 0.71516867876775, 0.072192315360733 },
    { 0.019330818715591, 0.11919477979462, 0.95053215224966 },
}
hsluv.refY = 1.0
hsluv.refU = 0.19783000664283
hsluv.refV = 0.46831999493879
hsluv.kappa = 903.2962962
hsluv.epsilon = 0.0088564516

return hsluv

function(tuple)
    local h = "#"
    for i = 1, 3 do
        local c = math.floor(tuple[i] * 255 + 0.5)
        local digit2 = math.fmod(c, 16)
        local x = (c - digit2) / 16
        local digit1 = math.floor(x)
        h = h .. string.sub(hexChars, digit1 + 1, digit1 + 1)
        h = h .. string.sub(hexChars, digit2 + 1, digit2 + 1)
    end
    return h
end

local M = {}

---@alias ColorSpec string RGB Hex string
---@alias ColorTable table<string, ColorSpec>
---@alias KansoColorsSpec { palette: ColorTable, theme: ColorTable }
---@alias KansoColors { palette: PaletteColors, theme: ThemeColors }

--- default config
---@class KansoConfig
M.config = {
    bold = true,
    italics = true,
    undercurl = true,
    commentStyle = { italic = true },
    functionStyle = {},
    keywordStyle = { italic = true },
    statementStyle = {},
    typeStyle = {},
    transparent = false,
    dimInactive = false,
    terminalColors = true,
    colors = { theme = { zen = {}, pearl = {}, ink = {}, all = {} }, palette = {} },
    ---@type fun(colors: KansoColorsSpec): table<string, table>
    overrides = function()
        return {}
    end,
    ---@type { dark: string, light: string }
    background = { dark = "ink", light = "pearl" },
    theme = "ink",
    ---@type { dark: "default"|"contrast", light: "default"|"contrast" }|"default"|"contrast"
    foreground = "default",
    compile = false,
}

local function check_config(_)
    local err
    return not err
end

--- update global configuration with user settings
---@param config? KansoConfig user configuration
function M.setup(config)
    if check_config(config) then
        M.config = vim.tbl_deep_extend("force", M.config, config or {})
    else
        vim.notify("Kanso: Errors found while loading user config. Using default config.", vim.log.levels.ERROR)
    end
end

--- load the colorscheme
---@param theme? string
function M.load(theme)
    local utils = require("kanso.utils")

    theme = theme or M.config.background[vim.o.background] or M.config.theme
    M._CURRENT_THEME = theme

    if vim.g.colors_name then
        vim.cmd("hi clear")
    end

    vim.g.colors_name = "kanso"
    vim.o.termguicolors = true

    -- Setup autocommand to reload theme when background changes
    if not M._autocmd_created then
        M._autocmd_created = true
        vim.api.nvim_create_autocmd("OptionSet", {
            pattern = "background",
            callback = function()
                if vim.g.colors_name == "kanso" then
                    -- Clear cached modules to force reload
                    package.loaded["kanso.colors"] = nil
                    package.loaded["kanso.themes"] = nil
                    M.load()
                end
            end,
        })
    end

    if M.config.compile then
        if utils.load_compiled(theme) then
            return
        end

        M.compile()
        utils.load_compiled(theme)
    else
        local foreground_setting = type(M.config.foreground) == "table" and M.config.foreground[vim.o.background]
            or M.config.foreground
        ---@cast foreground_setting "default"|"contrast"
        local colors =
            require("kanso.colors").setup({ theme = theme, colors = M.config.colors, foreground = foreground_setting })
        local highlights = require("kanso.highlights").setup(colors, M.config)
        require("kanso.highlights").highlight(highlights, M.config.terminalColors and colors.theme.term or {})
    end
end

function M.compile()
    for theme, _ in pairs(require("kanso.themes")) do
        -- Compile both foreground variants if foreground is a table
        if type(M.config.foreground) == "table" then
            -- Compile for dark mode
            local colors_dark = require("kanso.colors").setup({
                theme = theme,
                colors = M.config.colors,
                foreground = M.config.foreground.dark,
            })
            local highlights_dark = require("kanso.highlights").setup(colors_dark, M.config)
            require("kanso.utils").compile(
                theme .. "_dark_" .. M.config.foreground.dark,
                highlights_dark,
                M.config.terminalColors and colors_dark.theme.term or {}
            )

            -- Compile for light mode
            local colors_light = require("kanso.colors").setup({
                theme = theme,
                colors = M.config.colors,
                foreground = M.config.foreground.light,
            })
            local highlights_light = require("kanso.highlights").setup(colors_light, M.config)
            require("kanso.utils").compile(
                theme .. "_light_" .. M.config.foreground.light,
                highlights_light,
                M.config.terminalColors and colors_light.theme.term or {}
            )
        else
            -- Fallback for backward compatibility
            local foreground_str = M.config.foreground
            ---@cast foreground_str "default"|"contrast"
            local colors = require("kanso.colors").setup({
                theme = theme,
                colors = M.config.colors,
                foreground = foreground_str,
            })
            local highlights = require("kanso.highlights").setup(colors, M.config)
            require("kanso.utils").compile(theme, highlights, M.config.terminalColors and colors.theme.term or {})
        end
    end
end

vim.api.nvim_create_user_command("KansoCompile", function()
    for mod, _ in pairs(package.loaded) do
        if mod:match("^kanso%.") then
            package.loaded[mod] = nil
        end
    end
    M.compile()
    vim.notify("Kanso: compiled successfully!", vim.log.levels.INFO)
    M.load(M._CURRENT_THEME)
    vim.api.nvim_exec_autocmds("ColorScheme", { modeline = false })
end, {})

return M

This code segment functions to: Convert normalized RGB color values into a hexadecimal string representation by scaling each component to integer values and mapping them to corresponding hexadecimal characters.

```lua
[TASK_BEGIN]
function(tuple)
    local function to_hex(c)
        c = math.max(0, math.min(1, c))
        return string.format("%02x", math.floor(c * 255 + 0.5))
    end
    return "#" .. to_hex(tuple[1]) .. to_hex(tuple[2]) .. to_hex(tuple[3])
end
[TASK_END]
```