package database

import (
	"context"
	"log"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
)

// DB wraps the database connection pool
type DB struct {
	Pool *pgxpool.Pool
}

// Connect creates a new database connection pool
func Connect(databaseURL string) (*DB, error) {
	config, err := pgxpool.ParseConfig(databaseURL)
	if err != nil {
		return nil, err
	}

	// Configure connection pool
	config.MaxConns = 25
	config.MinConns = 5
	config.MaxConnLifetime = time.Hour
	config.MaxConnIdleTime = 30 * time.Minute
	config.HealthCheckPeriod = time.Minute

	pool, err := pgxpool.NewWithConfig(context.Background(), config)
	if err != nil {
		return nil, err
	}

	// Test connection
	if err := pool.Ping(context.Background()); err != nil {
		return nil, err
	}

	log.Println("Database connection established")
	return &DB{Pool: pool}, nil
}

// Close closes the database connection pool
func (db *DB) Close() {
	db.Pool.Close()
}

// Migrate runs database migrations
func Migrate(db *DB) error {
	ctx := context.Background()

	migrations := []string{
		// School Years
		`CREATE TABLE IF NOT EXISTS school_years (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			name VARCHAR(20) NOT NULL,
			start_date DATE NOT NULL,
			end_date DATE NOT NULL,
			is_current BOOLEAN DEFAULT false,
			teacher_id UUID NOT NULL,
			created_at TIMESTAMPTZ DEFAULT NOW()
		)`,

		// Classes
		`CREATE TABLE IF NOT EXISTS classes (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			teacher_id UUID NOT NULL,
			school_year_id UUID REFERENCES school_years(id),
			name VARCHAR(20) NOT NULL,
			grade_level INT NOT NULL,
			school_type VARCHAR(30),
			federal_state VARCHAR(50),
			created_at TIMESTAMPTZ DEFAULT NOW(),
			UNIQUE(teacher_id, school_year_id, name)
		)`,

		// Students
		`CREATE TABLE IF NOT EXISTS students (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			class_id UUID REFERENCES classes(id) ON DELETE CASCADE,
			first_name VARCHAR(100) NOT NULL,
			last_name VARCHAR(100) NOT NULL,
			birth_date DATE,
			student_number VARCHAR(50),
			notes TEXT,
			created_at TIMESTAMPTZ DEFAULT NOW()
		)`,

		// Subjects
		`CREATE TABLE IF NOT EXISTS subjects (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			teacher_id UUID NOT NULL,
			name VARCHAR(100) NOT NULL,
			short_name VARCHAR(10),
			is_main_subject BOOLEAN DEFAULT false,
			created_at TIMESTAMPTZ DEFAULT NOW(),
			UNIQUE(teacher_id, name)
		)`,

		// Exams
		`CREATE TABLE IF NOT EXISTS exams (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			teacher_id UUID NOT NULL,
			class_id UUID REFERENCES classes(id),
			subject_id UUID REFERENCES subjects(id),
			title VARCHAR(255) NOT NULL,
			exam_type VARCHAR(30) NOT NULL,
			topic VARCHAR(255),
			content TEXT,
			source_file_path VARCHAR(500),
			difficulty_level INT DEFAULT 3,
			duration_minutes INT,
			max_points DECIMAL(5,2),
			is_template BOOLEAN DEFAULT false,
			parent_exam_id UUID REFERENCES exams(id),
			status VARCHAR(20) DEFAULT 'draft',
			exam_date DATE,
			created_at TIMESTAMPTZ DEFAULT NOW(),
			updated_at TIMESTAMPTZ DEFAULT NOW()
		)`,

		// Exam Results
		`CREATE TABLE IF NOT EXISTS exam_results (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			exam_id UUID REFERENCES exams(id) ON DELETE CASCADE,
			student_id UUID REFERENCES students(id) ON DELETE CASCADE,
			points_achieved DECIMAL(5,2),
			grade DECIMAL(2,1),
			percentage DECIMAL(5,2),
			notes TEXT,
			is_absent BOOLEAN DEFAULT false,
			needs_rewrite BOOLEAN DEFAULT false,
			approved_by_teacher BOOLEAN DEFAULT false,
			approved_at TIMESTAMPTZ,
			created_at TIMESTAMPTZ DEFAULT NOW(),
			updated_at TIMESTAMPTZ DEFAULT NOW(),
			UNIQUE(exam_id, student_id)
		)`,

		// Grade Overview
		`CREATE TABLE IF NOT EXISTS grade_overview (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			student_id UUID REFERENCES students(id) ON DELETE CASCADE,
			subject_id UUID REFERENCES subjects(id),
			school_year_id UUID REFERENCES school_years(id),
			semester INT NOT NULL,
			written_grade_avg DECIMAL(3,2),
			written_grade_count INT DEFAULT 0,
			oral_grade DECIMAL(3,2),
			oral_notes TEXT,
			final_grade DECIMAL(3,2),
			final_grade_locked BOOLEAN DEFAULT false,
			written_weight INT DEFAULT 60,
			oral_weight INT DEFAULT 40,
			created_at TIMESTAMPTZ DEFAULT NOW(),
			updated_at TIMESTAMPTZ DEFAULT NOW(),
			UNIQUE(student_id, subject_id, school_year_id, semester)
		)`,

		// Attendance
		`CREATE TABLE IF NOT EXISTS attendance (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			student_id UUID REFERENCES students(id) ON DELETE CASCADE,
			date DATE NOT NULL,
			status VARCHAR(20) NOT NULL,
			periods INT DEFAULT 1,
			reason TEXT,
			created_at TIMESTAMPTZ DEFAULT NOW(),
			UNIQUE(student_id, date)
		)`,

		// Gradebook Entries
		`CREATE TABLE IF NOT EXISTS gradebook_entries (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			class_id UUID REFERENCES classes(id) ON DELETE CASCADE,
			student_id UUID REFERENCES students(id),
			date DATE NOT NULL,
			entry_type VARCHAR(30) NOT NULL,
			content TEXT NOT NULL,
			is_visible_to_parents BOOLEAN DEFAULT false,
			created_at TIMESTAMPTZ DEFAULT NOW()
		)`,

		// Certificates
		`CREATE TABLE IF NOT EXISTS certificates (
			id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
			student_id UUID REFERENCES students(id) ON DELETE CASCADE,
			school_year_id UUID REFERENCES school_years(id),
			semester INT NOT NULL,
			certificate_type VARCHAR(30),
			template_name VARCHAR(100),
			grades_json JSONB,
			remarks TEXT,
			absence_days INT DEFAULT 0,
			absence_days_unexcused INT DEFAULT 0,
			generated_pdf_path VARCHAR(500),
			status VARCHAR(20) DEFAULT 'draft',
			created_at TIMESTAMPTZ DEFAULT NOW(),
			updated_at TIMESTAMPTZ DEFAULT NOW()
		)`,

		// Indexes
		`CREATE INDEX IF NOT EXISTS idx_students_class ON students(class_id)`,
		`CREATE INDEX IF NOT EXISTS idx_exams_teacher ON exams(teacher_id)`,
		`CREATE INDEX IF NOT EXISTS idx_exams_class ON exams(class_id)`,
		`CREATE INDEX IF NOT EXISTS idx_exam_results_exam ON exam_results(exam_id)`,
		`CREATE INDEX IF NOT EXISTS idx_exam_results_student ON exam_results(student_id)`,
		`CREATE INDEX IF NOT EXISTS idx_grade_overview_student ON grade_overview(student_id)`,
		`CREATE INDEX IF NOT EXISTS idx_attendance_student ON attendance(student_id)`,
		`CREATE INDEX IF NOT EXISTS idx_attendance_date ON attendance(date)`,
		`CREATE INDEX IF NOT EXISTS idx_gradebook_class ON gradebook_entries(class_id)`,
	}

	for _, migration := range migrations {
		_, err := db.Pool.Exec(ctx, migration)
		if err != nil {
			log.Printf("Migration error: %v\nSQL: %s", err, migration)
			return err
		}
	}

	log.Println("Database migrations completed")
	return nil
}