package store

import (
	"database/sql"
	"encoding/json"
	"errors"
	"time"

	"task-dashboard/internal/models"
)

// ErrNativeTaskNotFound is returned by CompleteNativeTask, UncompleteNativeTask,
// and RescheduleNativeTask when no row matches the given id -- previously these
// three silently reported success on a 0-row UPDATE (Exec's err is nil even when
// no rows match), so a stale or wrong id from a caller looked identical to a real
// completion: the HTTP response was 200, but nothing in the database changed.
var ErrNativeTaskNotFound = errors.New("native task not found")

// GetNativeTasks returns all non-completed native tasks.
func (s *Store) GetNativeTasks() ([]models.Task, error) {
	rows, err := s.db.Query(`
		SELECT id, content, description, project_name, due_date, priority, completed, labels, created_at
		FROM native_tasks
		WHERE completed = 0
		ORDER BY CASE WHEN due_date IS NULL THEN 1 ELSE 0 END, due_date ASC, priority DESC
	`)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()
	return scanNativeTasks(rows)
}

// GetNativeTasksByDateRange returns non-completed native tasks due within the given range.
func (s *Store) GetNativeTasksByDateRange(start, end time.Time) ([]models.Task, error) {
	rows, err := s.db.Query(`
		SELECT id, content, description, project_name, due_date, priority, completed, labels, created_at
		FROM native_tasks
		WHERE completed = 0 AND due_date IS NOT NULL AND due_date >= ? AND due_date < ?
		ORDER BY due_date ASC, priority DESC
	`, start, end)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()
	return scanNativeTasks(rows)
}

// GetUndatedNativeTasks returns non-completed native tasks with no due date.
func (s *Store) GetUndatedNativeTasks() ([]models.Task, error) {
	rows, err := s.db.Query(`
		SELECT id, content, description, project_name, due_date, priority, completed, labels, created_at
		FROM native_tasks
		WHERE completed = 0 AND due_date IS NULL
		ORDER BY priority DESC, created_at ASC
	`)
	if err != nil {
		return nil, err
	}
	defer func() { _ = rows.Close() }()
	return scanNativeTasks(rows)
}

// CreateNativeTask inserts a new native task.
func (s *Store) CreateNativeTask(task models.Task) error {
	labelsJSON, _ := json.Marshal(task.Labels)
	_, err := s.db.Exec(`
		INSERT INTO native_tasks (id, content, description, project_name, due_date, priority, labels, created_at, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
	`, task.ID, task.Content, task.Description, task.ProjectName, task.DueDate, task.Priority, string(labelsJSON))
	return err
}

// UpdateNativeTask updates a native task's content and description.
func (s *Store) UpdateNativeTask(id, content, description string) error {
	_, err := s.db.Exec(`
		UPDATE native_tasks SET content = ?, description = ?, updated_at = CURRENT_TIMESTAMP
		WHERE id = ?
	`, content, description, id)
	return err
}

// CompleteNativeTask marks a task as completed. Returns ErrNativeTaskNotFound
// if id doesn't match any row.
func (s *Store) CompleteNativeTask(id string) error {
	result, err := s.db.Exec(`
		UPDATE native_tasks SET completed = 1, updated_at = CURRENT_TIMESTAMP WHERE id = ?
	`, id)
	if err != nil {
		return err
	}
	return checkRowsAffected(result)
}

// RescheduleNativeTask sets a new due date on a task. Returns
// ErrNativeTaskNotFound if id doesn't match any row.
func (s *Store) RescheduleNativeTask(id string, dueDate time.Time) error {
	result, err := s.db.Exec(`
		UPDATE native_tasks SET due_date = ?, updated_at = CURRENT_TIMESTAMP WHERE id = ?
	`, dueDate, id)
	if err != nil {
		return err
	}
	return checkRowsAffected(result)
}

// UncompleteNativeTask marks a task as not completed. Returns
// ErrNativeTaskNotFound if id doesn't match any row.
func (s *Store) UncompleteNativeTask(id string) error {
	result, err := s.db.Exec(`
		UPDATE native_tasks SET completed = 0, updated_at = CURRENT_TIMESTAMP WHERE id = ?
	`, id)
	if err != nil {
		return err
	}
	return checkRowsAffected(result)
}

// checkRowsAffected returns ErrNativeTaskNotFound if the update matched no
// rows -- mirrors the RowsAffected() check already used in sqlite.go's
// ApproveAgentSession/DenyAgentSession for the same "silent 0-row update"
// class of bug.
func checkRowsAffected(result sql.Result) error {
	affected, err := result.RowsAffected()
	if err != nil {
		return err
	}
	if affected == 0 {
		return ErrNativeTaskNotFound
	}
	return nil
}

func scanNativeTasks(rows interface {
	Next() bool
	Scan(...interface{}) error
	Err() error
}) ([]models.Task, error) {
	var tasks []models.Task
	for rows.Next() {
		var t models.Task
		var labelsJSON string
		var dueDateStr *string
		if err := rows.Scan(&t.ID, &t.Content, &t.Description, &t.ProjectName, &dueDateStr, &t.Priority, &t.Completed, &labelsJSON, &t.CreatedAt); err != nil {
			return nil, err
		}
		if dueDateStr != nil {
			if parsed, err := time.Parse(time.RFC3339, *dueDateStr); err == nil {
				t.DueDate = &parsed
			} else if parsed, err := time.Parse("2006-01-02 15:04:05", *dueDateStr); err == nil {
				t.DueDate = &parsed
			} else if parsed, err := time.Parse("2006-01-02", *dueDateStr); err == nil {
				t.DueDate = &parsed
			}
		}
		if err := json.Unmarshal([]byte(labelsJSON), &t.Labels); err != nil {
			t.Labels = nil
		}
		tasks = append(tasks, t)
	}
	return tasks, rows.Err()
}