package repository

import (
	"context"
	"errors"
	"fmt"

	dbgen "Yimaru-Backend/gen/db"
	"github.com/jackc/pgx/v5"
)

// CompleteLessonForUser records lesson completion for sequential lesson gating and
// re-evaluates higher-level practice-based rollups.
func (s *Store) CompleteLessonForUser(ctx context.Context, userID, lessonID int64) error {
	q, tx, err := s.BeginTx(ctx)
	if err != nil {
		return fmt.Errorf("begin tx: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	if err := q.InsertUserLessonProgress(ctx, dbgen.InsertUserLessonProgressParams{UserID: userID, LessonID: lessonID}); err != nil {
		return err
	}
	lesson, err := q.GetLessonByID(ctx, lessonID)
	if err != nil {
		return err
	}
	mod, err := q.GetModuleByID(ctx, lesson.ModuleID)
	if err != nil {
		return err
	}
	crs, err := q.GetCourseByID(ctx, mod.CourseID)
	if err != nil {
		return err
	}

	if err := s.cascadeLMSCompletion(ctx, q, userID, &mod.ID, crs.ID, crs.ProgramID); err != nil {
		return err
	}

	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("commit: %w", err)
	}
	return nil
}

// CompletePracticeForUser records practice completion and cascades practice-based
// completion upward when all published practices in scope are complete.
func (s *Store) CompletePracticeForUser(ctx context.Context, userID, questionSetID int64) error {
	q, tx, err := s.BeginTx(ctx)
	if err != nil {
		return fmt.Errorf("begin tx: %w", err)
	}
	defer func() { _ = tx.Rollback(ctx) }()

	if _, err := q.MarkPracticeCompleted(ctx, dbgen.MarkPracticeCompletedParams{
		UserID:        userID,
		QuestionSetID: questionSetID,
	}); err != nil {
		return err
	}

	scope, err := q.GetPracticeScopeByQuestionSetID(ctx, questionSetID)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			// Exam-prep practices are not in lms_practices; completion is tracked in user_practice_progress only.
			if err := tx.Commit(ctx); err != nil {
				return fmt.Errorf("commit: %w", err)
			}
			return nil
		}
		return err
	}
	var (
		moduleID *int64
		courseID int64
	)
	switch {
	case scope.ModuleID.Valid:
		mid := scope.ModuleID.Int64
		moduleID = &mid
		mod, err := q.GetModuleByID(ctx, mid)
		if err != nil {
			return err
		}
		courseID = mod.CourseID
	case scope.LessonID.Valid:
		lesson, err := q.GetLessonByID(ctx, scope.LessonID.Int64)
		if err != nil {
			return err
		}
		mid := lesson.ModuleID
		moduleID = &mid
		mod, err := q.GetModuleByID(ctx, mid)
		if err != nil {
			return err
		}
		courseID = mod.CourseID
	case scope.CourseID.Valid:
		courseID = scope.CourseID.Int64
	default:
		return fmt.Errorf("practice %d is not linked to lesson/module/course", questionSetID)
	}

	crs, err := q.GetCourseByID(ctx, courseID)
	if err != nil {
		return err
	}

	if err := s.cascadeLMSCompletion(ctx, q, userID, moduleID, crs.ID, crs.ProgramID); err != nil {
		return err
	}

	if err := tx.Commit(ctx); err != nil {
		return fmt.Errorf("commit: %w", err)
	}
	return nil
}

func (s *Store) cascadeLMSCompletion(ctx context.Context, q *dbgen.Queries, userID int64, moduleID *int64, courseID, programID int64) error {
	if moduleID != nil {
		modulePracticesTotal, err := q.CountPublishedPracticesInModule(ctx, toPgInt8(moduleID))
		if err != nil {
			return err
		}
		modulePracticesDone, err := q.CountUserCompletedPublishedPracticesInModule(ctx, dbgen.CountUserCompletedPublishedPracticesInModuleParams{
			ModuleID: toPgInt8(moduleID),
			UserID:   userID,
		})
		if err != nil {
			return err
		}

		modulePracticesComplete := modulePracticesTotal > 0 && modulePracticesDone >= modulePracticesTotal
		if !modulePracticesComplete {
			return nil
		}

		if err := q.InsertUserModuleProgress(ctx, dbgen.InsertUserModuleProgressParams{UserID: userID, ModuleID: *moduleID}); err != nil {
			return err
		}
	}

	nMods, err := q.CountModulesInCourse(ctx, courseID)
	if err != nil {
		return err
	}
	nDoneMods, err := q.CountUserCompletedModulesInCourse(ctx, dbgen.CountUserCompletedModulesInCourseParams{
		CourseID: courseID,
		UserID:   userID,
	})
	if err != nil {
		return err
	}

	coursePracticesTotal, err := q.CountPublishedPracticesInCourse(ctx, toPgInt8(&courseID))
	if err != nil {
		return err
	}
	coursePracticesDone, err := q.CountUserCompletedPublishedPracticesInCourse(ctx, dbgen.CountUserCompletedPublishedPracticesInCourseParams{
		CourseID: toPgInt8(&courseID),
		UserID:   userID,
	})
	if err != nil {
		return err
	}

	courseModulesComplete := nMods > 0 && nDoneMods >= nMods
	coursePracticesComplete := coursePracticesTotal > 0 && coursePracticesDone >= coursePracticesTotal
	if !courseModulesComplete || !coursePracticesComplete {
		return nil
	}

	if err := q.InsertUserCourseProgress(ctx, dbgen.InsertUserCourseProgressParams{UserID: userID, CourseID: courseID}); err != nil {
		return err
	}

	nCr, err := q.CountCoursesInProgram(ctx, programID)
	if err != nil {
		return err
	}
	nCrDone, err := q.CountUserCompletedCoursesInProgram(ctx, dbgen.CountUserCompletedCoursesInProgramParams{
		ProgramID: programID,
		UserID:    userID,
	})
	if err != nil {
		return err
	}

	programPracticesTotal, err := q.CountPublishedPracticesInProgram(ctx, programID)
	if err != nil {
		return err
	}
	programPracticesDone, err := q.CountUserCompletedPublishedPracticesInProgram(ctx, dbgen.CountUserCompletedPublishedPracticesInProgramParams{
		ProgramID: programID,
		UserID:    userID,
	})
	if err != nil {
		return err
	}

	programCoursesComplete := nCr > 0 && nCrDone >= nCr
	programPracticesComplete := programPracticesTotal > 0 && programPracticesDone >= programPracticesTotal
	if !programCoursesComplete || !programPracticesComplete {
		return nil
	}

	if err := q.InsertUserProgramProgress(ctx, dbgen.InsertUserProgramProgressParams{UserID: userID, ProgramID: programID}); err != nil {
		return err
	}

	return nil
}