use std::collections::HashMap;

use futures::future::BoxFuture;
use headless_lms_utils::numbers::f32_to_three_decimals;
use url::Url;

use crate::{
    exams,
    exercise_service_info::{get_service_info_by_exercise_type, ExerciseServiceInfoApi},
    exercise_services::{get_exercise_service_by_exercise_type, get_internal_grade_url},
    exercise_task_submissions::ExerciseTaskSubmission,
    exercise_tasks::{self, ExerciseTask},
    exercises::{Exercise, GradingProgress},
    library::custom_view_exercises::CustomViewExerciseTaskGrading,
    prelude::*,
    user_exercise_states::UserExerciseState,
    CourseOrExamId,
};

#[derive(Debug, Serialize, Deserialize, PartialEq, Clone)]
#[cfg_attr(feature = "ts_rs", derive(TS))]
pub struct ExerciseTaskGrading {
    pub id: Uuid,
    pub created_at: DateTime<Utc>,
    pub updated_at: DateTime<Utc>,
    pub exercise_task_submission_id: Uuid,
    pub course_id: Option<Uuid>,
    pub exam_id: Option<Uuid>,
    pub exercise_id: Uuid,
    pub exercise_task_id: Uuid,
    pub grading_priority: i32,
    pub score_given: Option<f32>,
    pub grading_progress: GradingProgress,
    pub unscaled_score_given: Option<f32>,
    pub unscaled_score_maximum: Option<i32>,
    pub grading_started_at: Option<DateTime<Utc>>,
    pub grading_completed_at: Option<DateTime<Utc>>,
    pub feedback_json: Option<serde_json::Value>,
    pub feedback_text: Option<String>,
    pub deleted_at: Option<DateTime<Utc>>,
}

#[derive(Debug, Serialize, PartialEq, Eq, Clone)]
pub struct ExerciseTaskGradingRequest<'a> {
    pub grading_update_url: &'a str,
    pub exercise_spec: &'a Option<serde_json::Value>,
    pub submission_data: &'a Option<serde_json::Value>,
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Clone)]
#[cfg_attr(feature = "ts_rs", derive(TS))]
pub struct ExerciseTaskGradingResult {
    pub grading_progress: GradingProgress,
    pub score_given: f32,
    pub score_maximum: i32,
    pub feedback_text: Option<String>,
    pub feedback_json: Option<serde_json::Value>,
    #[serde(skip_serializing_if = "Option::is_none")] // Allows us to omit the field in typescript
    pub set_user_variables: Option<HashMap<String, serde_json::Value>>,
}

#[derive(Debug, Serialize, Deserialize, PartialEq, Eq, Clone, Copy, sqlx::Type)]
#[cfg_attr(feature = "ts_rs", derive(TS))]
#[sqlx(type_name = "user_points_update_strategy", rename_all = "kebab-case")]
pub enum UserPointsUpdateStrategy {
    CanAddPointsButCannotRemovePoints,
    CanAddPointsAndCanRemovePoints,
}

pub async fn insert(
    conn: &mut PgConnection,
    pkey_policy: PKeyPolicy<Uuid>,
    submission_id: Uuid,
    course_id: Uuid,
    exercise_id: Uuid,
    exercise_task_id: Uuid,
) -> ModelResult<Uuid> {
    let res = sqlx::query!(
        "
INSERT INTO exercise_task_gradings (
    id,
    exercise_task_submission_id,
    course_id,
    exercise_id,
    exercise_task_id
  )
VALUES ($1, $2, $3, $4, $5)
RETURNING id
        ",
        pkey_policy.into_uuid(),
        submission_id,
        course_id,
        exercise_id,
        exercise_task_id
    )
    .fetch_one(conn)
    .await?;
    Ok(res.id)
}

pub async fn get_by_id(conn: &mut PgConnection, id: Uuid) -> ModelResult<ExerciseTaskGrading> {
    let res = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
SELECT id,
  created_at,
  updated_at,
  exercise_task_submission_id,
  course_id,
  exam_id,
  exercise_id,
  exercise_task_id,
  grading_priority,
  score_given,
  grading_progress as "grading_progress: _",
  unscaled_score_maximum,
  unscaled_score_given,
  grading_started_at,
  grading_completed_at,
  feedback_json,
  feedback_text,
  deleted_at
FROM exercise_task_gradings
WHERE id = $1
"#,
        id
    )
    .fetch_one(conn)
    .await?;
    Ok(res)
}

pub async fn get_by_exercise_task_submission_id(
    conn: &mut PgConnection,
    exercise_task_submission_id: Uuid,
) -> ModelResult<Option<ExerciseTaskGrading>> {
    let res = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
SELECT id,
  created_at,
  updated_at,
  exercise_task_submission_id,
  course_id,
  exam_id,
  exercise_id,
  exercise_task_id,
  grading_priority,
  score_given,
  grading_progress as "grading_progress: _",
  unscaled_score_maximum,
  unscaled_score_given,
  grading_started_at,
  grading_completed_at,
  feedback_json,
  feedback_text,
  deleted_at
FROM exercise_task_gradings
WHERE exercise_task_submission_id = $1
  AND deleted_at IS NULL
        "#,
        exercise_task_submission_id,
    )
    .fetch_optional(conn)
    .await?;
    Ok(res)
}

pub async fn get_total_score_given_for_exercise_slide_submission(
    conn: &mut PgConnection,
    exercise_slide_submission_id: &Uuid,
) -> ModelResult<Option<f32>> {
    let res = sqlx::query!(
        "
SELECT SUM(COALESCE(etg.score_given, 0))::real
FROM exercise_task_gradings etg
  JOIN exercise_task_submissions ets ON etg.exercise_task_submission_id = ets.id
WHERE ets.exercise_slide_submission_id = $1
  AND etg.deleted_at IS NULL
  AND ets.deleted_at IS NULL
        ",
        exercise_slide_submission_id
    )
    .fetch_one(conn)
    .await?;
    Ok(res.sum)
}

/// For now gets this information from some task submission in a slide submission.
pub async fn get_point_update_strategy_from_gradings(
    conn: &mut PgConnection,
    exercise_slide_submission_id: &Uuid,
) -> ModelResult<GradingProgress> {
    let res = sqlx::query!(
        r#"
SELECT etg.grading_progress as "grading_progress: GradingProgress"
FROM exercise_task_gradings etg
  JOIN exercise_task_submissions ets ON etg.exercise_task_submission_id = ets.id
WHERE ets.exercise_slide_submission_id = $1
  AND etg.deleted_at IS NULL
  AND ets.deleted_at IS NULL
LIMIT 1
    "#,
        exercise_slide_submission_id
    )
    .fetch_one(conn)
    .await?;
    Ok(res.grading_progress)
}

pub async fn get_course_id(conn: &mut PgConnection, id: Uuid) -> ModelResult<Option<Uuid>> {
    let course_id = sqlx::query!(
        "
SELECT course_id
from exercise_task_gradings
where id = $1
        ",
        id
    )
    .fetch_one(conn)
    .await?
    .course_id;
    Ok(course_id)
}

pub async fn get_course_or_exam_id(
    conn: &mut PgConnection,
    id: Uuid,
) -> ModelResult<CourseOrExamId> {
    let res = sqlx::query!(
        "
SELECT course_id,
  exam_id
from exercise_task_gradings
where id = $1
",
        id
    )
    .fetch_one(conn)
    .await?;
    CourseOrExamId::from(res.course_id, res.exam_id)
}

pub async fn new_grading(
    conn: &mut PgConnection,
    exercise: &Exercise,
    submission: &ExerciseTaskSubmission,
) -> ModelResult<ExerciseTaskGrading> {
    let grading = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
INSERT INTO exercise_task_gradings(
    exercise_task_submission_id,
    course_id,
    exam_id,
    exercise_id,
    exercise_task_id,
    grading_started_at
  )
VALUES($1, $2, $3, $4, $5, now())
RETURNING id,
  created_at,
  updated_at,
  exercise_task_submission_id,
  course_id,
  exam_id,
  exercise_id,
  exercise_task_id,
  grading_priority,
  score_given,
  grading_progress as "grading_progress: _",
  unscaled_score_given,
  unscaled_score_maximum,
  grading_started_at,
  grading_completed_at,
  feedback_json,
  feedback_text,
  deleted_at
"#,
        submission.id,
        exercise.course_id,
        exercise.exam_id,
        exercise.id,
        submission.exercise_task_id,
    )
    .fetch_one(conn)
    .await?;
    Ok(grading)
}

pub async fn set_grading_progress(
    conn: &mut PgConnection,
    id: Uuid,
    grading_progress: GradingProgress,
) -> ModelResult<()> {
    sqlx::query!(
        "
UPDATE exercise_task_gradings
SET grading_progress = $1
WHERE id = $2
",
        grading_progress as GradingProgress,
        id
    )
    .execute(conn)
    .await?;
    Ok(())
}

#[allow(clippy::too_many_arguments)]
pub async fn grade_submission(
    conn: &mut PgConnection,
    submission: &ExerciseTaskSubmission,
    exercise_task: &ExerciseTask,
    exercise: &Exercise,
    grading: &ExerciseTaskGrading,
    user_exercise_state: &UserExerciseState,
    fetch_service_info: impl Fn(Url) -> BoxFuture<'static, ModelResult<ExerciseServiceInfoApi>>,
    send_grading_request: impl Fn(
        Url,
        &ExerciseTask,
        &ExerciseTaskSubmission,
    ) -> BoxFuture<'static, ModelResult<ExerciseTaskGradingResult>>,
) -> ModelResult<ExerciseTaskGrading> {
    let exercise_service_info =
        get_service_info_by_exercise_type(conn, &exercise_task.exercise_type, fetch_service_info)
            .await?;
    let exercise_service =
        get_exercise_service_by_exercise_type(conn, &exercise_task.exercise_type).await?;
    let grade_url = get_internal_grade_url(&exercise_service, &exercise_service_info).await?;
    let exercise_task_grading_result =
        send_grading_request(grade_url, exercise_task, submission).await?;
    let mut tx = conn.begin().await?;
    let updated_grading =
        update_grading(&mut tx, grading, &exercise_task_grading_result, exercise).await?;
    crate::user_course_instance_exercise_service_variables::insert_after_exercise_task_graded(
        &mut tx,
        &exercise_task_grading_result.set_user_variables,
        exercise_task,
        user_exercise_state,
    )
    .await?;
    tx.commit().await?;
    Ok(updated_grading)
}

pub async fn update_grading(
    conn: &mut PgConnection,
    grading: &ExerciseTaskGrading,
    grading_result: &ExerciseTaskGradingResult,
    exercise: &Exercise,
) -> ModelResult<ExerciseTaskGrading> {
    let grading_completed_at = if grading_result.grading_progress.is_complete() {
        Some(Utc::now())
    } else {
        None
    };
    let exercise_slide_id = exercise_tasks::get_exercise_task_by_id(conn, grading.exercise_task_id)
        .await?
        .exercise_slide_id;
    let exercise_task_count =
        exercise_tasks::get_exercise_tasks_by_exercise_slide_ids(conn, &[exercise_slide_id])
            .await?
            .len() as f32;
    let correctness_coefficient =
        grading_result.score_given / (grading_result.score_maximum as f32);
    // ensure the score doesn't go over the maximum
    let score_given_with_all_decimals = f32::min(
        (exercise.score_maximum as f32) * correctness_coefficient / exercise_task_count,
        exercise.score_maximum as f32 / exercise_task_count,
    );
    // Scores are rounded to two decimals
    let score_given_rounded = f32_to_three_decimals(score_given_with_all_decimals);
    let grading = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
UPDATE exercise_task_gradings
SET grading_progress = $2,
  unscaled_score_given = $3,
  unscaled_score_maximum = $4,
  feedback_text = $5,
  feedback_json = $6,
  grading_completed_at = $7,
  score_given = $8
WHERE id = $1
RETURNING id,
  created_at,
  updated_at,
  exercise_task_submission_id,
  course_id,
  exam_id,
  exercise_id,
  exercise_task_id,
  grading_priority,
  score_given,
  grading_progress as "grading_progress: _",
  unscaled_score_given,
  unscaled_score_maximum,
  grading_started_at,
  grading_completed_at,
  feedback_json,
  feedback_text,
  deleted_at
"#,
        grading.id,
        grading_result.grading_progress as GradingProgress,
        grading_result.score_given,
        grading_result.score_maximum,
        grading_result.feedback_text,
        grading_result.feedback_json,
        grading_completed_at,
        score_given_rounded
    )
    .fetch_one(conn)
    .await?;

    Ok(grading)
}

/// Fetches the grading for the student, but hides the result in some circumstances.
/// For example, for an ongoing exam.
pub async fn get_for_student(
    conn: &mut PgConnection,
    grading_id: Uuid,
    user_id: Uuid,
) -> ModelResult<Option<ExerciseTaskGrading>> {
    let grading = get_by_id(conn, grading_id).await?;
    if let Some(exam_id) = grading.exam_id {
        let exam = exams::get(conn, exam_id).await?;
        let enrollment = exams::get_enrollment(conn, exam_id, user_id)
            .await?
            .ok_or_else(|| {
                ModelError::new(
                    ModelErrorType::Generic,
                    "User has grading for exam but no enrollment".to_string(),
                    None,
                )
            })?;
        if Utc::now() > enrollment.started_at + chrono::Duration::minutes(exam.time_minutes.into())
            || exam.ends_at.map(|ea| Utc::now() > ea).unwrap_or_default()
        {
            // exam over, return grading
            Ok(Some(grading))
        } else {
            // exam still ongoing, do not return grading
            Ok(None)
        }
    } else {
        Ok(Some(grading))
    }
}

pub async fn get_all_gradings_by_exercise_slide_submission_id(
    conn: &mut PgConnection,
    exercise_slide_submission_id: Uuid,
) -> ModelResult<Vec<ExerciseTaskGrading>> {
    let res = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
SELECT id,
created_at,
updated_at,
exercise_task_submission_id,
course_id,
exam_id,
exercise_id,
exercise_task_id,
grading_priority,
score_given,
grading_progress as "grading_progress: _",
unscaled_score_given,
unscaled_score_maximum,
grading_started_at,
grading_completed_at,
feedback_json,
feedback_text,
deleted_at
FROM exercise_task_gradings
WHERE deleted_at IS NULL
  AND exercise_task_submission_id IN (
    SELECT id
    FROM exercise_task_submissions
    WHERE exercise_slide_submission_id = $1
  )
"#,
        exercise_slide_submission_id
    )
    .fetch_all(&mut *conn)
    .await?;
    Ok(res)
}

pub async fn get_new_and_old_exercise_task_gradings_by_regrading_id(
    conn: &mut PgConnection,
    regrading_id: Uuid,
) -> ModelResult<HashMap<Uuid, ExerciseTaskGrading>> {
    let res = sqlx::query_as!(
        ExerciseTaskGrading,
        r#"
SELECT id,
  created_at,
  updated_at,
  exercise_task_submission_id,
  course_id,
  exam_id,
  exercise_id,
  exercise_task_id,
  grading_priority,
  score_given,
  grading_progress as "grading_progress: _",
  unscaled_score_given,
  unscaled_score_maximum,
  grading_started_at,
  grading_completed_at,
  feedback_json,
  feedback_text,
  deleted_at
FROM exercise_task_gradings
WHERE deleted_at IS NULL
  AND id IN (
    SELECT etrs.grading_before_regrading
    FROM exercise_task_regrading_submissions etrs
    WHERE etrs.deleted_at IS NULL
      AND etrs.regrading_id = $1
    UNION
    SELECT etrs.grading_after_regrading
    FROM exercise_task_regrading_submissions etrs
    WHERE etrs.grading_after_regrading IS NOT NULL
      AND etrs.deleted_at IS NULL
      AND etrs.regrading_id = $1
  );
    "#,
        regrading_id
    )
    .fetch_all(conn)
    .await?;
    let mut map = HashMap::with_capacity(res.len());
    for regrading in res {
        map.insert(regrading.id, regrading);
    }
    Ok(map)
}

// Get all gradings for user for course module and exercise type
pub async fn get_user_exercise_task_gradings_by_module_and_exercise_type(
    conn: &mut PgConnection,
    user_id: Uuid,
    exercise_type: &str,
    module_id: Uuid,
    course_instance_id: Uuid,
) -> ModelResult<Vec<CustomViewExerciseTaskGrading>> {
    let res: Vec<CustomViewExerciseTaskGrading> = sqlx::query_as!(
        CustomViewExerciseTaskGrading,
        r#"
SELECT etg.id,
  etg.created_at,
  etg.exercise_id,
  etg.exercise_task_id,
  etg.feedback_json,
  etg.feedback_text
FROM exercise_task_gradings etg
  JOIN exercise_tasks et ON etg.exercise_task_id = et.id
  JOIN exercise_task_submissions ets ON etg.exercise_task_submission_id = ets.id
  JOIN exercise_slide_submissions ess ON ets.exercise_slide_submission_id = ess.id
  JOIN exercises e ON ess.exercise_id = e.id
  JOIN chapters c ON e.chapter_id = c.id
WHERE etg.deleted_at IS NULL
  AND et.deleted_at IS NULL
  AND et.exercise_type = $2
  AND ess.user_id = $1
  AND ess.course_instance_id = $4
  AND ess.deleted_at IS NULL
  AND e.deleted_at IS NULL
  AND c.deleted_at IS NULL
  AND c.course_module_id = $3
      "#,
        user_id,
        exercise_type,
        module_id,
        course_instance_id
    )
    .fetch_all(conn)
    .await?;
    Ok(res)
}