package main

import (
	"database/sql"
	"encoding/json"
	"net/http"
	"strconv"

	"github.com/go-chi/chi/v5"
)

func createTodo(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var input CreateTodo
		if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		priority := int64(1)
		if input.Priority != nil {
			priority = *input.Priority
		}
		status := "pending"
		if input.Status != nil {
			status = *input.Status
		}
		var todo Todo
		err := db.QueryRow(
			`INSERT INTO todos (title, description, due_date, priority, status)
			 VALUES (?, ?, ?, ?, ?)
			 RETURNING id, title, description, due_date, priority, status`,
			input.Title, input.Description, input.DueDate, priority, status,
		).Scan(&todo.ID, &todo.Title, &todo.Description, &todo.DueDate, &todo.Priority, &todo.Status)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusCreated)
		json.NewEncoder(w).Encode(todo)
	}
}

func listTodos(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rows, err := db.Query("SELECT id, title, description, due_date, priority, status FROM todos")
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		defer rows.Close()
		var todos []Todo
		for rows.Next() {
			var t Todo
			if err := rows.Scan(&t.ID, &t.Title, &t.Description, &t.DueDate, &t.Priority, &t.Status); err != nil {
				http.Error(w, err.Error(), http.StatusInternalServerError)
				return
			}
			todos = append(todos, t)
		}
		if todos == nil {
			todos = []Todo{}
		}
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(todos)
	}
}

func getTodo(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, _ := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		var todo Todo
		err := db.QueryRow(
			"SELECT id, title, description, due_date, priority, status FROM todos WHERE id = ?", id,
		).Scan(&todo.ID, &todo.Title, &todo.Description, &todo.DueDate, &todo.Priority, &todo.Status)
		if err == sql.ErrNoRows {
			http.Error(w, "not found", http.StatusNotFound)
			return
		}
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(todo)
	}
}

func updateTodo(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, _ := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		var existing Todo
		err := db.QueryRow(
			"SELECT id, title, description, due_date, priority, status FROM todos WHERE id = ?", id,
		).Scan(&existing.ID, &existing.Title, &existing.Description, &existing.DueDate, &existing.Priority, &existing.Status)
		if err == sql.ErrNoRows {
			http.Error(w, "not found", http.StatusNotFound)
			return
		}
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		var input UpdateTodo
		if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
		if input.Title != nil {
			existing.Title = *input.Title
		}
		if input.Description != nil {
			existing.Description = input.Description
		}
		if input.DueDate != nil {
			existing.DueDate = input.DueDate
		}
		if input.Priority != nil {
			existing.Priority = *input.Priority
		}
		if input.Status != nil {
			existing.Status = *input.Status
		}
		var updated Todo
		err = db.QueryRow(
			`UPDATE todos SET title = ?, description = ?, due_date = ?, priority = ?, status = ?
			 WHERE id = ?
			 RETURNING id, title, description, due_date, priority, status`,
			existing.Title, existing.Description, existing.DueDate, existing.Priority, existing.Status, id,
		).Scan(&updated.ID, &updated.Title, &updated.Description, &updated.DueDate, &updated.Priority, &updated.Status)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(updated)
	}
}

func deleteTodo(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, _ := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		result, err := db.Exec("DELETE FROM todos WHERE id = ?", id)
		if err != nil {
			http.Error(w, err.Error(), http.StatusInternalServerError)
			return
		}
		rows, _ := result.RowsAffected()
		if rows == 0 {
			http.Error(w, "not found", http.StatusNotFound)
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}