using Dates

# Date — 仅日期（无时间）
d = Date(2026, 5, 11)
println(d)  # 2026-05-11

# DateTime — 日期+时间
dt = DateTime(2026, 5, 11, 14, 30, 0)
println(dt)  # 2026-05-11T14:30:00

# Time — 仅时间（无日期）
t = Time(14, 30, 0)
println(t)  # 14:30:00

# 当前时间
println(now())       # DateTime
println(today())     # Date
println(now(Time))   # Time

# AbstractDateTime
# ├── TimeType
# │   ├── Date        — 日期
# │   └── DateTime    — 日期时间
# └── Time            — 时间（独立）

# 从字符串构造
d1 = Date("2026-05-11")
dt1 = DateTime("2026-05-11T14:30:00")
t1 = Time("14:30:00")

# 使用关键字参数
d2 = Date(2026, 5)
dt2 = DateTime(2026, 5, 11, 14)

# 从 Unix 时间戳
epoch = DateTime(1970, 1, 1)
dt_from_ts = epoch + Second(1715428200)

# 自定义格式解析
d = Date("11/05/2026", dateformat"dd/mm/yyyy")
println(d)  # 2026-05-11

dt = DateTime("2026年05月11日 14:30", dateformat"yyyy年mm月dd日 HH:MM")
println(dt)

# 中文日期解析
d2 = Date("2026年5月11日", dateformat"yyyy年m月d日")

d = Date(2026, 5, 11)

# 使用 format 函数
println(Dates.format(d, dateformat"yyyy-mm-dd"))    # 2026-05-11
println(Dates.format(d, dateformat"dd/mm/yyyy"))    # 11/05/2026
println(Dates.format(d, dateformat"yyyy年mm月dd日")) # 2026年05月11日

dt = DateTime(2026, 5, 11, 14, 30, 45)
println(Dates.format(dt, dateformat"yyyy-mm-dd HH:MM:SS"))
# 2026-05-11 14:30:45

# dayname / dayofweek
println(Dates.dayname(d))   # Sunday (或中文系统下的星期日)
println(Dates.dayofweek(d)) # 7

using Dates

d = Date(2026, 1, 15)

# Period 类型
d + Day(1)      # +1天
d + Week(2)     # +2周
d + Month(3)    # +3月
d + Year(1)     # +1年

# 减法
d - Day(10)

# 组合运算
d + Month(1) + Day(15)  # 2026-03-02

d1 = Date(2026, 1, 1)
d2 = Date(2026, 12, 31)

# 日期差
diff = d2 - d1
println(typeof(diff))  # Day
println(value(diff))   # 364

# 转换为不同单位
diff_days = Dates.value(Day(d2 - d1))
diff_weeks = diff_days ÷ 7

# DateTime 差值
dt1 = DateTime(2026, 1, 1, 0, 0, 0)
dt2 = DateTime(2026, 1, 1, 12, 30, 0)
diff = dt2 - dt1
println(typeof(diff))  # Millisecond

d1 = Date(2026, 1, 1)
d2 = Date(2026, 6, 15)

println(d1 < d2)    # true
println(d1 == d2)   # false
println(d1 > d2)    # false

# min / max
println(min(d1, d2))  # 2026-01-01
println(max(d1, d2))  # 2026-06-15

using TimeZones

# 创建带时区的时间
utc = ZonedDateTime(DateTime(2026, 5, 11, 14, 0), tz"UTC")
shanghai = astimezone(utc, tz"Asia/Shanghai")
println(shanghai)  # 2026-05-11T22:00:00+08:00

# 时区转换
nyc = astimezone(utc, tz"America/New_York")
tokyo = astimezone(utc, tz"Asia/Tokyo")

println("UTC:      $utc")
println("上海:     $shanghai")
println("纽约:     $nyc")
println("东京:     $tokyo")

# 获取当前时区时间
now_shanghai = now(tz"Asia/Shanghai")
println("上海现在: $now_shanghai")

# 常用时区标识
# tz"UTC"           协调世界时
# tz"Asia/Shanghai"  中国标准时间 (UTC+8)
# tz"Asia/Tokyo"     日本标准时间 (UTC+9)
# tz"America/New_York" 美国东部时间
# tz"Europe/London"    英国时间

# 列出所有时区
# TimeZone[]  # 所有可用时区

# 等间隔日期序列
dates = Date(2026, 1, 1):Day(1):Date(2026, 1, 10)
for d in dates
    println(d)
end
# 2026-01-01
# 2026-01-02
# ...
# 2026-01-10

# 月度序列
months = Date(2026, 1, 1):Month(1):Date(2026, 12, 1)
println(collect(months))  # 12个月的第一天

# 年度序列
years = Date(2020, 1, 1):Year(1):Date(2026, 1, 1)

# 所有工作日
function workdays(start::Date, stop::Date)
    return filter(d -> Dates.dayofweek(d) <= 5, start:Day(1):stop)
end

wdays = workdays(Date(2026, 5, 1), Date(2026, 5, 31))
println("5月工作日: $(length(wdays)) 天")

# 月末日期
function month_ends(year)
    return [Dates.lastdayofmonth(Date(year, m, 1)) for m in 1:12]
end

println(month_ends(2026))

d = DateTime(2026, 5, 11, 14, 30, 45)

println(year(d))        # 2026
println(month(d))       # 5
println(day(d))         # 11
println(hour(d))        # 14
println(minute(d))      # 30
println(second(d))      # 45
println(dayofweek(d))   # 1 (Monday=1)
println(dayofyear(d))   # 131
println(week(d))        # 19
println(daysinmonth(d)) # 31
println(isleapyear(d))  # false

# @elapsed 返回执行时间（秒）
t = @elapsed sum(1:1_000_000)
println("耗时: $(round(t*1000, digits=2)) ms")

# @timev 提供详细计时信息
@timev begin
    data = rand(1000, 1000)
    result = data * data'
    s = sum(result)
end
# 输出：
#   0.123456 seconds (15 allocations: 15.259 MiB)
#   elapsed time (ns): 123456789
#   gc time (ns):      1234567
#   bytes allocated:   16000000
#   pool allocs:       15

# @time 基本计时
@time result = sum(sin(x) for x in 1:10_000_000)
# 0.345678 seconds (4 allocations: 160 bytes)

using BenchmarkTools

# @btime 自动多次运行取最优
@btime sum(1:1_000_000)
# 1.234 ms (0 allocations)

# @benchmark 详细统计
@benchmark sin(1.0)
# 输出最小、中位数、平均、最大时间

# 精确比较两种实现
@btime [sin(x) for x in 1:1000]     # 分配内存
@btime collect(sin(x) for x in 1:1000)  # 生成器

using Dates

# 每日数据
dates = Date(2026, 1, 1):Day(1):Date(2026, 12, 31)
values = cumsum(randn(length(dates)))  # 随机游走

# 每周聚合
function weekly_average(dates, values)
    weeks = Dict{Date, Vector{Float64}}()
    for (d, v) in zip(dates, values)
        week_start = d - Day(Dates.dayofweek(d) - 1)
        push!(get!(weeks, week_start, Float64[]), v)
    end
    sorted_weeks = sort(collect(weeks))
    return ([w for (w, _) in sorted_weeks],
            [mean(vs) for (_, vs) in sorted_weeks])
end

using Statistics
weekly_dates, weekly_vals = weekly_average(dates, values)
println("周平均值数量: $(length(weekly_dates))")

# 工作日判断
is_workday(d::Date) = Dates.dayofweek(d) <= 5

# 计算交易日
function trading_days(start::Date, stop::Date)
    return filter(is_workday, start:Day(1):stop)
end

# N个交易日后
function add_trading_days(d::Date, n::Int)
    current = d
    added = 0
    while added < n
        current += Day(1)
        if is_workday(current)
            added += 1
        end
    end
    return current
end

start = Date(2026, 1, 1)
result = add_trading_days(start, 20)
println("20个交易日后: $result")

function monthly_stats(dates, values)
    monthly = Dict{Tuple{Int,Int}, Vector{Float64}}()
    for (d, v) in zip(dates, values)
        key = (year(d), month(d))
        push!(get!(monthly, key, Float64[]), v)
    end
    
    for (ym, vals) in sort(collect(monthly))
        println("$(ym[1])-$(lpad(ym[2], 2, '0')): " *
                "均值=$(round(mean(vals), digits=2)), " *
                "标准差=$(round(std(vals), digits=2))")
    end
end