use chrono::{Datelike, Duration, Local, NaiveDate};
pub fn run(args_json: &str) -> String {
let args: super::tool_param_types::DateCalcArgs = match serde_json::from_str(args_json) {
Ok(a) => a,
Err(e) => return format!("参数 JSON 无效: {e}"),
};
match args
.mode
.unwrap_or(super::tool_param_types::DateCalcMode::Offset)
{
super::tool_param_types::DateCalcMode::Diff => run_diff(&args),
super::tool_param_types::DateCalcMode::Offset => run_offset(&args),
}
}
fn parse_date(s: &str) -> Option<NaiveDate> {
NaiveDate::parse_from_str(s.trim(), "%Y-%m-%d").ok()
}
fn run_diff(args: &super::tool_param_types::DateCalcArgs) -> String {
let from_str = match args.from.as_deref() {
Some(s) if !s.trim().is_empty() => s.trim(),
_ => return "错误：diff 模式需要 from 参数（YYYY-MM-DD）".to_string(),
};
let to_str = match args.to.as_deref() {
Some(s) if !s.trim().is_empty() => s.trim(),
_ => return "错误：diff 模式需要 to 参数（YYYY-MM-DD）".to_string(),
};
let from = match parse_date(from_str) {
Some(d) => d,
None => return format!("错误：无法解析 from 日期 {:?}（格式 YYYY-MM-DD）", from_str),
};
let to = match parse_date(to_str) {
Some(d) => d,
None => return format!("错误：无法解析 to 日期 {:?}（格式 YYYY-MM-DD）", to_str),
};
let diff = to.signed_duration_since(from);
let days = diff.num_days();
let weeks = days / 7;
let rem_days = days % 7;
format!(
"从 {} 到 {}：\n- 共 {} 天\n- 约 {} 周 {} 天",
from,
to,
days,
weeks,
rem_days.abs()
)
}
fn run_offset(args: &super::tool_param_types::DateCalcArgs) -> String {
let base_str = args.base.as_deref().unwrap_or("");
let base = if base_str.trim().is_empty() {
Local::now().date_naive()
} else {
match parse_date(base_str) {
Some(d) => d,
None => return format!("错误：无法解析 base 日期 {:?}（格式 YYYY-MM-DD）", base_str),
}
};
let offset_str = match args.offset.as_deref() {
Some(s) if !s.trim().is_empty() => s.trim(),
_ => return "错误：offset 模式需要 offset 参数（如 +30d, -2w, +1m）".to_string(),
};
let (sign, rest) = if let Some(r) = offset_str.strip_prefix('+') {
(1i64, r)
} else if let Some(r) = offset_str.strip_prefix('-') {
(-1i64, r)
} else {
(1i64, offset_str)
};
let Some((unit_start, _)) = rest.char_indices().last() else {
return format!("错误：无法解析偏移量 {:?}", offset_str);
};
let (num_str, unit) = rest.split_at(unit_start);
let num: i64 = match num_str.parse::<i64>() {
Ok(n) => n * sign,
Err(_) => return format!("错误：无法解析偏移量数值 {:?}", offset_str),
};
let result = match unit {
"d" => base + Duration::days(num),
"w" => base + Duration::weeks(num),
"m" => {
let month = base.month0() as i32 + num as i32;
let year = base.year() + month.div_euclid(12);
let m = (month.rem_euclid(12) + 1) as u32;
let d = base.day().min(days_in_month(year, m));
NaiveDate::from_ymd_opt(year, m, d).unwrap_or(base)
}
_ => return format!("错误：未知偏移单位 {:?}（支持 d/w/m）", unit),
};
format!(
"基准：{}\n偏移：{}\n结果：{}\n星期：{}",
base,
offset_str,
result,
result.format("%A")
)
}
fn days_in_month(year: i32, month: u32) -> u32 {
NaiveDate::from_ymd_opt(
if month == 12 { year + 1 } else { year },
if month == 12 { 1 } else { month + 1 },
1,
)
.map(|d| d.pred_opt().map(|p| p.day()).unwrap_or(28))
.unwrap_or(28)
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn diff_basic() {
let out = run(r#"{"mode":"diff","from":"2024-01-01","to":"2024-01-31"}"#);
assert!(out.contains("30 天"), "out={}", out);
}
#[test]
fn offset_days() {
let out = run(r#"{"mode":"offset","base":"2024-03-01","offset":"+10d"}"#);
assert!(out.contains("2024-03-11"), "out={}", out);
}
#[test]
fn offset_weeks() {
let out = run(r#"{"mode":"offset","base":"2024-01-01","offset":"+2w"}"#);
assert!(out.contains("2024-01-15"), "out={}", out);
}
#[test]
fn offset_negative() {
let out = run(r#"{"mode":"offset","base":"2024-03-15","offset":"-15d"}"#);
assert!(out.contains("2024-02-29"), "out={}", out);
}
#[test]
fn missing_offset() {
let out = run(r#"{"mode":"offset","base":"2024-01-01"}"#);
assert!(out.contains("错误"));
}
}