package com.kyndryl.platform.service;

import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.*;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicLong;

/**
 * A minimal but fully functional CRUD REST API for "items".
 *
 * Endpoints:
 *   GET  /api/items       — list all items
 *   POST /api/items       — create an item   { "name": "...", "description": "..." }
 *   GET  /api/items/{id}  — get single item
 *   PUT  /api/items/{id}  — update item
 *   DELETE /api/items/{id} — delete item
 *
 * Health + metrics are exposed via Spring Actuator at /actuator/health and
 * /actuator/prometheus (see application.yml).
 */
@RestController
@RequestMapping("/api/items")
public class ItemsController {

    record Item(long id, String name, String description) {}

    private final Map<Long, Item> store = new ConcurrentHashMap<>();
    private final AtomicLong counter = new AtomicLong(1);

    @GetMapping
    public Collection<Item> list() {
        return store.values();
    }

    @PostMapping
    @ResponseStatus(HttpStatus.CREATED)
    public Item create(@RequestBody Map<String, String> body) {
        long id = counter.getAndIncrement();
        Item item = new Item(id,
            body.getOrDefault("name", "unnamed"),
            body.getOrDefault("description", ""));
        store.put(id, item);
        return item;
    }

    @GetMapping("/{id}")
    public Item get(@PathVariable long id) {
        Item item = store.get(id);
        if (item == null) throw new NoSuchElementException("Item not found: " + id);
        return item;
    }

    @PutMapping("/{id}")
    public Item update(@PathVariable long id, @RequestBody Map<String, String> body) {
        if (!store.containsKey(id)) throw new NoSuchElementException("Item not found: " + id);
        Item updated = new Item(id,
            body.getOrDefault("name", store.get(id).name()),
            body.getOrDefault("description", store.get(id).description()));
        store.put(id, updated);
        return updated;
    }

    @DeleteMapping("/{id}")
    public Map<String, Object> delete(@PathVariable long id) {
        store.remove(id);
        return Map.of("deleted", id);
    }
}