use serde::{Serialize, Deserialize};
use std::io::{Read, Write};
use std::fs::File;
use std::time::{SystemTime, UNIX_EPOCH, Duration};
use std::ops::{Add, Sub};
use clap::Parser;
use chrono::{TimeZone, Local, Timelike};

#[derive(Debug, Parser)]
struct Flags {
   #[arg(short = 'f', long = "file")]
   f: String,

   #[arg(short = 'l', long = "log")]
   log: bool,

   #[arg(short = 's', long = "since")]
   since: Option<String>,

   #[arg(short = 'a', long = "add")]
   add: Option<String>,

   #[arg(short = 't', long = "tag")]
   tag: Option<String>,
}

fn main() {
   let flags = Flags::parse();

   add(&flags.f, &flags.add, &flags.tag).unwrap();
   log(&flags.f, &flags.log, &flags.since).unwrap();
}

fn add(f: &String, x: &Option<String>, tag: &Option<String>) -> Result<(), String> {
   match x {
      Some(x) => {
         let mut tsheet = load(&f)?;
         tsheet.add(
            x.to_string(),
            tag.clone().unwrap_or("".to_string()),
         );
         save(&f, tsheet)?;
      },
      None => {},
   };
   Ok(())
}

#[derive(Debug, Serialize, Clone)]
struct Log {
   t: String,
   d: f32,
   xs: Vec<LogX>,
}
#[derive(Debug, Serialize, Clone)]
struct LogX {
   d: f32,
   x: String,
}

fn log(f: &String, enabled: &bool, since: &Option<String>) -> Result<(), String> {
   if !enabled {
      return Ok(());
   }
   let since = parse_time(since)?;
   let tsheet = load(&f)?;
   let tsheet = tsheet.since(since);
   let tsheet = tsheet.sorted();

   let mut result = vec![];
   let mut curr = Log{t: "".to_string(), d: 0.0, xs: vec![]};
   for i in 0..tsheet.xs.len() {
      let x = &tsheet.xs[i];
      if curr.t != x.timestamp() {
         if curr.xs.len() > 0 {
            result.push(curr.clone());
         }
         curr.xs.truncate(0);
         curr.t = x.timestamp();
         curr.d = 0.0;
      }
      let d = match curr.xs.len() {
         0 if x.x.len() == 0 => 0.0,
         0 => 1.0,
         _ => ((tsheet.xs[i].t - tsheet.xs[i-1].t) as f32 / (60.0*60.0)) as f32,
      };
      curr.t = x.timestamp();
      curr.xs.push(LogX{d: d, x: x.x.clone()});
   }
   if curr.xs.len() > 0 {
      result.push(curr.clone());
   }
   for i in result.iter_mut() {
      i.d = i.xs.iter().map(|x| x.d).sum();
   }

   for log in result {
      for x in log.xs {
         if x.x.len() > 0 {
            println!("{} ({}) {} ({:.1})", log.t, (0.5 + log.d) as i64, x.x, x.d + 0.05);
         }
      }
   }
   Ok(())
}

fn parse_time(since: &Option<String>) -> Result<SystemTime, String> {
   match since {
      Some(since) => {
         match chrono::NaiveDate::parse_from_str(since, "%Y-%m-%d") {
            Ok(nd) => {
               let ndt = nd.and_hms_opt(1, 1, 1).unwrap();
               let dt = Local.from_local_datetime(&ndt).unwrap();
               Ok(UNIX_EPOCH.add(
                  Duration::from_secs(dt.timestamp() as u64)
               ))
            },
            Err(msg) => Err(format!("failed to parse {}: {}", since, msg)),
         }
      },
      None => Ok(SystemTime::now().sub(Duration::from_secs(Local::now().hour() as u64*60*60))),
   }
}

#[derive(Debug, PartialEq, Serialize, Deserialize)]
struct TSheet {
   xs: Vec<X>,
}

#[derive(Debug, PartialEq, Serialize, Deserialize, Clone, Ord, Eq, PartialOrd)]
struct X {
   t: i64,
   x: String,
   tag: String,
}

fn save(path: &String, tsheet: TSheet) -> Result<(), String> {
   match File::create(path.clone()) {
      Ok(mut writer) => _save(&mut writer, tsheet),
      Err(reason) => Err(format!("failed to open {} to save tsheet: {}", path, reason)),
   }
}

fn _save(writer: &mut dyn Write, tsheet: TSheet) -> Result<(), String> {
   let mut w = serde_yaml::Serializer::new(writer);
   match tsheet.serialize(&mut w) {
      Ok(_) => Ok(()),
      Err(reason) => Err(format!("failed to serialize tsheet: {}", reason)),
   }
}

fn load(path: &String) -> Result<TSheet, String> {
   match File::open(path.clone()) {
      Ok(mut reader) => _load(&mut reader),
      Err(reason) => Err(format!("failed to read tsheet {}: {}", path, reason)),
   }
}

fn _load(reader: &mut dyn Read) -> Result<TSheet, String> {
   match serde_yaml::from_reader::<&mut dyn Read, TSheet>(reader) {
      Ok(tsheet) => Ok(tsheet),
      Err(err) => Err(format!("failed to parse tsheet: {}", err)),
   }
}

#[cfg(test)]
mod test_save_load {
   use super::*;

   #[test]
   fn test_empty() {
      let got = _load(&mut "xs: []".as_bytes()).expect("failed to parse 'xs: []' tsheet");
      assert_eq!(got, TSheet{xs: vec![]});

      let mut w = vec![];
      _save(&mut w, got).expect("failed saving tsheet to writer");
      assert_eq!(String::from_utf8(w).unwrap(), "xs: []\n".to_string());
   }

   #[test]
   fn test_testdata_standalone_yaml() {
      let want = TSheet{xs: vec![
         X{t: 1, x: "def".to_string(), tag: "abc".to_string()},
         X{t: 2, x: "ghi".to_string(), tag: "".to_string()},
      ]};
      assert_eq!(
         load(&"./src/testdata/standalone.yaml".to_string()).expect("cant load standalone.yaml"),
         want,
      );

      let mut w = vec![];
      _save(&mut w, want).expect("failed saving tsheet to writer");
      assert_eq!(String::from_utf8(w).unwrap(), "xs:\n- t: 1\n  x: def\n  tag: abc\n- t: 2\n  x: ghi\n  tag: ''\n".to_string());
   }
}

impl TSheet {
   fn since(&self, t: SystemTime) -> TSheet {
      let mut result = TSheet{xs: vec![]};
      self.xs.iter()
         .filter(|x| x.ts() >= t)
         .for_each(|x| result.xs.push(x.clone()));
      result
   }

   fn add(&mut self, x: String, tag: String) {
      self.xs.push(new_x(SystemTime::now(), x, tag));
   }

   fn sorted(&self) -> TSheet {
      let mut result = TSheet{xs: self.xs.clone()};
      result.xs.sort();
      return result;
   }
}

impl X {
   fn ts(&self) -> SystemTime {
      UNIX_EPOCH.add(Duration::from_secs(self.t.try_into().unwrap()))
   }

   fn timestamp(&self) -> String {
      let dt = Local.timestamp_opt(self.t, 0).unwrap();
      dt.format("%Y-%m-%d").to_string()
   }
}

fn new_x(t: SystemTime, x: String, tag: String) -> X {
   X{
      t: t.duration_since(UNIX_EPOCH).unwrap().as_secs() as i64,
      x: x,
      tag: tag,
   }
}

#[cfg(test)]
mod test_tsheet {
   use super::*;

   #[test]
   fn test_add() {
      let mut given = TSheet{xs: vec![
         X{t: 1, x: "def".to_string(), tag: "abc".to_string()},
      ]};
      given.add("ghi".to_string(), "".to_string());
      assert_eq!(given.xs.len(), 2);
      assert!(given.xs[1].t != 1);
      assert_eq!(given.xs[1].x, "ghi".to_string());
      assert_eq!(given.xs[1].tag, "".to_string());
   }

   #[test]
   fn test_since_date() {
      let given = TSheet{xs: vec![
         X{t: 1, x: "def".to_string(), tag: "abc".to_string()},
         X{t: 2, x: "ghi".to_string(), tag: "".to_string()},
         X{t: 3, x: "jkl".to_string(), tag: "".to_string()},
      ]};
      let want = TSheet{xs: vec![
         X{t: 2, x: "ghi".to_string(), tag: "".to_string()},
         X{t: 3, x: "jkl".to_string(), tag: "".to_string()},
      ]};
      let got = given.since(UNIX_EPOCH.add(Duration::from_secs(2)));
      assert_eq!(got, want);
   }
}