use crate::utils::ProcessingBatch;
use meilisearch_types::milli::progress::{AtomicSubStep, NamedStep, Progress, ProgressView, Step};
use roaring::RoaringBitmap;
use std::{borrow::Cow, sync::Arc};

#[derive(Clone)]
pub struct ProcessingTasks {
    pub batch: Option<Arc<ProcessingBatch>>,
    /// The list of tasks ids that are currently running.
    pub processing: Arc<RoaringBitmap>,
    /// The progress on processing tasks
    pub progress: Option<Progress>,
}

impl ProcessingTasks {
    /// Creates an empty `ProcessingAt` struct.
    pub fn new() -> ProcessingTasks {
        ProcessingTasks { batch: None, processing: Arc::new(RoaringBitmap::new()), progress: None }
    }

    pub fn get_progress_view(&self) -> Option<ProgressView> {
        Some(self.progress.as_ref()?.as_progress_view())
    }

    /// Stores the currently processing tasks, and the date time at which it started.
    pub fn start_processing(
        &mut self,
        processing_batch: ProcessingBatch,
        processing: RoaringBitmap,
    ) -> Progress {
        self.batch = Some(Arc::new(processing_batch));
        self.processing = Arc::new(processing);
        let progress = Progress::default();
        progress.update_progress(BatchProgress::ProcessingTasks);
        self.progress = Some(progress.clone());

        progress
    }

    /// Set the processing tasks to an empty list
    pub fn stop_processing(&mut self) -> Self {
        self.progress = None;

        Self {
            batch: std::mem::take(&mut self.batch),
            processing: std::mem::take(&mut self.processing),
            progress: None,
        }
    }

    /// Returns `true` if there, at least, is one task that is currently processing that we must stop.
    pub fn must_cancel_processing_tasks(&self, canceled_tasks: &RoaringBitmap) -> bool {
        !self.processing.is_disjoint(canceled_tasks)
    }
}

#[repr(u8)]
#[derive(Copy, Clone)]
pub enum BatchProgress {
    ProcessingTasks,
    WritingTasksToDisk,
}

impl Step for BatchProgress {
    fn name(&self) -> Cow<'static, str> {
        match self {
            BatchProgress::ProcessingTasks => Cow::Borrowed("processing tasks"),
            BatchProgress::WritingTasksToDisk => Cow::Borrowed("writing tasks to disk"),
        }
    }

    fn current(&self) -> u32 {
        *self as u8 as u32
    }

    fn total(&self) -> u32 {
        2
    }
}

#[derive(Default)]
pub struct Task {}

impl NamedStep for Task {
    fn name(&self) -> &'static str {
        "task"
    }
}
pub type AtomicTaskStep = AtomicSubStep<Task>;

#[cfg(test)]
mod test {
    use std::sync::atomic::Ordering;

    use meili_snap::{json_string, snapshot};

    use super::*;

    #[test]
    fn one_level() {
        let mut processing = ProcessingTasks::new();
        processing.start_processing(ProcessingBatch::new(0), RoaringBitmap::new());
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "processing tasks",
              "finished": 0,
              "total": 2
            }
          ],
          "percentage": 0.0
        }
        "#);
        processing.progress.as_ref().unwrap().update_progress(BatchProgress::WritingTasksToDisk);
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "writing tasks to disk",
              "finished": 1,
              "total": 2
            }
          ],
          "percentage": 50.0
        }
        "#);
    }

    #[test]
    fn task_progress() {
        let mut processing = ProcessingTasks::new();
        processing.start_processing(ProcessingBatch::new(0), RoaringBitmap::new());
        let (atomic, tasks) = AtomicTaskStep::new(10);
        processing.progress.as_ref().unwrap().update_progress(tasks);
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "processing tasks",
              "finished": 0,
              "total": 2
            },
            {
              "name": "task",
              "finished": 0,
              "total": 10
            }
          ],
          "percentage": 0.0
        }
        "#);
        atomic.fetch_add(6, Ordering::Relaxed);
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "processing tasks",
              "finished": 0,
              "total": 2
            },
            {
              "name": "task",
              "finished": 6,
              "total": 10
            }
          ],
          "percentage": 30.000002
        }
        "#);
        processing.progress.as_ref().unwrap().update_progress(BatchProgress::WritingTasksToDisk);
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "writing tasks to disk",
              "finished": 1,
              "total": 2
            }
          ],
          "percentage": 50.0
        }
        "#);
        let (atomic, tasks) = AtomicTaskStep::new(5);
        processing.progress.as_ref().unwrap().update_progress(tasks);
        atomic.fetch_add(4, Ordering::Relaxed);
        snapshot!(json_string!(processing.get_progress_view()), @r#"
        {
          "steps": [
            {
              "name": "writing tasks to disk",
              "finished": 1,
              "total": 2
            },
            {
              "name": "task",
              "finished": 4,
              "total": 5
            }
          ],
          "percentage": 90.0
        }
        "#);
    }
}