utils.lua

local M = {}

--- 将颜色字符串转为 RGB 数组
--- @param color string # 形如 "#RRGGBB" 的颜色字符串
--- @return table # {r, g, b}
local function rgb(color)
    color = string.lower(color)
    return {
        tonumber(color:sub(2, 3), 16),
        tonumber(color:sub(4, 5), 16),
        tonumber(color:sub(6, 7), 16),
    }
end

--- 前景色与背景色混合，返回混合后的 HEX 颜色
--- @param foreground string # 前景色 HEX
--- @param alpha number|string # 混合比例 (0~1) 或 16进制字符串
--- @param background string # 背景色 HEX
--- @return string # 混合后的 HEX 颜色
function M.blend(foreground, alpha, background)
    alpha = type(alpha) == 'string' and (tonumber(alpha, 16) / 0xff) or alpha
    local bg, fg = rgb(background), rgb(foreground)
    local function blendChannel(i)
        return math.floor(math.min(math.max(0, alpha * fg[i] + (1 - alpha) * bg[i]), 255) + 0.5)
    end
    return string.format('#%02x%02x%02x', blendChannel(1), blendChannel(2), blendChannel(3))
end

--- 判断主题类型（深色/浅色），并计算对比度等信息
--- @param bg_color string # 背景色 HEX
--- @param fg_color string # 前景色 HEX
--- @return table # { is_dark, contrast_ratio, background_luminance, foreground_luminance }
function M.detect_theme_type(bg_color, fg_color)
    local function complete_hex(hex)
        hex = hex:gsub('#', ''):lower()
        if #hex == 3 then
            hex = hex:gsub('(.)', '%1%1')
        end
        return '#' .. hex
    end

    local function safe_rgb(color)
        local ok, result = pcall(rgb, complete_hex(color))
        return ok and result or { 0, 0, 0 }
    end

    local bg = safe_rgb(bg_color)
    local bg_lum = 0.2126 * bg[1] + 0.7152 * bg[2] + 0.0722 * bg[3]

    local fg = safe_rgb(fg_color or '#ffffff')
    local fg_lum = 0.2126 * fg[1] + 0.7152 * fg[2] + 0.0722 * fg[3]

    return {
        is_dark = bg_lum < 128,
        contrast_ratio = (math.max(bg_lum, fg_lum) + 0.05) / (math.min(bg_lum, fg_lum) + 0.05),
        background_luminance = bg_lum,
        foreground_luminance = fg_lum,
    }
end

--- 获取当前操作系统类型，支持分发不同逻辑
--- @param handlers table|nil # 可选，系统分发表
--- @return string|unknown # 返回系统类型或分发结果
function M.get_os_type(handlers)
    local triple = require('wezterm').target_triple
    local sys
    if triple:find('darwin') then
        sys = 'macos'
    elseif triple:find('windows') then
        sys = 'windows'
    elseif triple:find('linux') then
        sys = 'linux'
    else
        sys = 'unknown'
    end

    if type(handlers) == 'table' then
        local handler = handlers[sys] or handlers['default']
        if type(handler) == 'function' then
            return handler()
        else
            return handler
        end
    end

    return sys
end

return M