// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.

use std::sync::atomic::AtomicU64;
use std::sync::atomic::Ordering;
use std::sync::Arc;
use std::time::SystemTime;

use deno_core::parking_lot::Mutex;
use deno_runtime::ops::tty::ConsoleSize;

use crate::colors;

use self::renderer::ProgressBarRenderer;
use self::renderer::ProgressData;
use self::renderer::ProgressDataDisplayEntry;

use super::draw_thread::DrawThread;
use super::draw_thread::DrawThreadGuard;
use super::draw_thread::DrawThreadRenderer;

mod renderer;

// Inspired by Indicatif, but this custom implementation allows
// for more control over what's going on under the hood.

pub struct UpdateGuard {
  maybe_entry: Option<ProgressBarEntry>,
}

impl Drop for UpdateGuard {
  fn drop(&mut self) {
    if let Some(entry) = &self.maybe_entry {
      entry.finish();
    }
  }
}

impl UpdateGuard {
  pub fn set_position(&self, value: u64) {
    if let Some(entry) = &self.maybe_entry {
      entry.set_position(value);
    }
  }

  pub fn set_total_size(&self, value: u64) {
    if let Some(entry) = &self.maybe_entry {
      entry.set_total_size(value);
    }
  }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ProgressBarStyle {
  DownloadBars,
  TextOnly,
}

#[derive(Clone, Debug)]
struct ProgressBarEntry {
  id: usize,
  pub message: String,
  pos: Arc<AtomicU64>,
  total_size: Arc<AtomicU64>,
  progress_bar: ProgressBarInner,
}

impl ProgressBarEntry {
  pub fn position(&self) -> u64 {
    self.pos.load(Ordering::Relaxed)
  }

  pub fn set_position(&self, new_pos: u64) {
    self.pos.store(new_pos, Ordering::Relaxed);
  }

  pub fn total_size(&self) -> u64 {
    self.total_size.load(Ordering::Relaxed)
  }

  pub fn set_total_size(&self, new_size: u64) {
    self.total_size.store(new_size, Ordering::Relaxed);
  }

  pub fn finish(&self) {
    self.progress_bar.finish_entry(self.id);
  }

  pub fn percent(&self) -> f64 {
    let pos = self.pos.load(Ordering::Relaxed) as f64;
    let total_size = self.total_size.load(Ordering::Relaxed) as f64;
    if total_size == 0f64 {
      0f64
    } else {
      pos / total_size
    }
  }
}

#[derive(Debug)]
struct InternalState {
  /// If this guard exists, then it means the progress
  /// bar is displaying in the draw thread.
  draw_thread_guard: Option<DrawThreadGuard>,
  start_time: SystemTime,
  keep_alive_count: usize,
  total_entries: usize,
  entries: Vec<ProgressBarEntry>,
}

#[derive(Clone, Debug)]
struct ProgressBarInner {
  state: Arc<Mutex<InternalState>>,
  renderer: Arc<dyn ProgressBarRenderer>,
}

impl ProgressBarInner {
  fn new(renderer: Arc<dyn ProgressBarRenderer>) -> Self {
    Self {
      state: Arc::new(Mutex::new(InternalState {
        draw_thread_guard: None,
        start_time: SystemTime::now(),
        keep_alive_count: 0,
        total_entries: 0,
        entries: Vec::new(),
      })),
      renderer,
    }
  }

  pub fn add_entry(&self, message: String) -> ProgressBarEntry {
    let mut internal_state = self.state.lock();
    let id = internal_state.total_entries;
    let entry = ProgressBarEntry {
      id,
      message,
      pos: Default::default(),
      total_size: Default::default(),
      progress_bar: self.clone(),
    };
    internal_state.entries.push(entry.clone());
    internal_state.total_entries += 1;
    internal_state.keep_alive_count += 1;

    self.maybe_start_draw_thread(&mut internal_state);

    entry
  }

  fn finish_entry(&self, entry_id: usize) {
    let mut internal_state = self.state.lock();

    if let Ok(index) = internal_state
      .entries
      .binary_search_by(|e| e.id.cmp(&entry_id))
    {
      internal_state.entries.remove(index);
      self.decrement_keep_alive(&mut internal_state);
    }
  }

  pub fn increment_clear(&self) {
    let mut internal_state = self.state.lock();
    internal_state.keep_alive_count += 1;
  }

  pub fn decrement_clear(&self) {
    let mut internal_state = self.state.lock();
    self.decrement_keep_alive(&mut internal_state);
  }

  fn decrement_keep_alive(&self, state: &mut InternalState) {
    state.keep_alive_count -= 1;

    if state.keep_alive_count == 0 {
      // drop the guard to remove this from the draw thread
      state.draw_thread_guard.take();
    }
  }

  fn maybe_start_draw_thread(&self, internal_state: &mut InternalState) {
    if internal_state.draw_thread_guard.is_none()
      && internal_state.keep_alive_count > 0
    {
      internal_state.start_time = SystemTime::now();
      internal_state.draw_thread_guard =
        Some(DrawThread::add_entry(0, Arc::new(self.clone())));
    }
  }
}

impl DrawThreadRenderer for ProgressBarInner {
  fn render(&self, size: &ConsoleSize) -> String {
    let data = {
      let state = self.state.lock();
      if state.entries.is_empty() {
        return String::new();
      }
      let preferred_entry = state
        .entries
        .iter()
        .find(|e| e.percent() > 0f64)
        .or_else(|| state.entries.iter().last())
        .unwrap();
      ProgressData {
        duration: state.start_time.elapsed().unwrap(),
        terminal_width: size.cols,
        pending_entries: state.entries.len(),
        total_entries: state.total_entries,
        display_entry: ProgressDataDisplayEntry {
          message: preferred_entry.message.clone(),
          position: preferred_entry.position(),
          total_size: preferred_entry.total_size(),
        },
        percent_done: {
          let mut total_percent_sum = 0f64;
          for entry in &state.entries {
            total_percent_sum += entry.percent();
          }
          total_percent_sum +=
            (state.total_entries - state.entries.len()) as f64;
          total_percent_sum / (state.total_entries as f64)
        },
      }
    };
    self.renderer.render(data)
  }
}

#[derive(Clone, Debug)]
pub struct ProgressBar {
  inner: Option<ProgressBarInner>,
}

impl ProgressBar {
  /// Checks if progress bars are supported
  pub fn are_supported() -> bool {
    DrawThread::is_supported()
  }

  pub fn new(style: ProgressBarStyle) -> Self {
    Self {
      inner: match Self::are_supported() {
        true => Some(ProgressBarInner::new(match style {
          ProgressBarStyle::DownloadBars => {
            Arc::new(renderer::BarProgressBarRenderer)
          }
          ProgressBarStyle::TextOnly => {
            Arc::new(renderer::TextOnlyProgressBarRenderer)
          }
        })),
        false => None,
      },
    }
  }

  pub fn update(&self, msg: &str) -> UpdateGuard {
    match &self.inner {
      Some(inner) => {
        let entry = inner.add_entry(msg.to_string());
        UpdateGuard {
          maybe_entry: Some(entry),
        }
      }
      None => {
        // if we're not running in TTY, fallback to using logger crate
        if !msg.is_empty() {
          log::log!(log::Level::Info, "{} {}", colors::green("Download"), msg);
        }
        UpdateGuard { maybe_entry: None }
      }
    }
  }

  pub fn clear_guard(&self) -> ClearGuard {
    if let Some(inner) = &self.inner {
      inner.increment_clear();
    }
    ClearGuard { pb: self.clone() }
  }

  fn decrement_clear(&self) {
    if let Some(inner) = &self.inner {
      inner.decrement_clear();
    }
  }
}

pub struct ClearGuard {
  pb: ProgressBar,
}

impl Drop for ClearGuard {
  fn drop(&mut self) {
    self.pb.decrement_clear();
  }
}