package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"
)

// invForwarder forwards plugin inventory events to the inventory service,
// porting main.py's _forward_to_inventory_service / _handle_inventory_delta.
// Only active in cutover (write) mode; nil in shadow/read-only mode, where the
// plugin firehose never carries inventory anyway.
//
//   full_inventory  -> POST {url}/process-inventory      (full replace)
//   inventory_delta add/update -> POST {url}/inventory/{char}/item
//   inventory_delta remove     -> DELETE {url}/inventory/{char}/item/{item_id}
//
// Deltas are fire-and-forget (never block the /ws/position read loop), serialized
// per-character (so a char's rapid deltas don't race the inventory DELETE+INSERT),
// and globally capped at 8 concurrent forwards.
type invForwarder struct {
	url       string
	client    *http.Client
	sem       chan struct{}
	mu        sync.Mutex
	locks     map[string]*sync.Mutex
	log       *slog.Logger
	broadcast func(map[string]any)
}

func newInvForwarder(rawURL string, log *slog.Logger, broadcast func(map[string]any)) *invForwarder {
	return &invForwarder{
		url:       strings.TrimRight(rawURL, "/"),
		client:    &http.Client{Timeout: 30 * time.Second},
		sem:       make(chan struct{}, 8),
		locks:     map[string]*sync.Mutex{},
		log:       log,
		broadcast: broadcast,
	}
}

func (f *invForwarder) charLock(name string) *sync.Mutex {
	f.mu.Lock()
	defer f.mu.Unlock()
	l := f.locks[name]
	if l == nil {
		l = &sync.Mutex{}
		f.locks[name] = l
	}
	return l
}

// forwardFullInventory POSTs a full inventory snapshot (full replace). Runs
// inline on the /ws/position handler — main.py awaits _store_inventory too.
func (f *invForwarder) forwardFullInventory(data map[string]any) {
	char := toStr(data["character_name"])
	body, _ := json.Marshal(map[string]any{
		"character_name": char,
		"timestamp":      data["timestamp"],
		"items":          data["items"],
	})
	resp, err := f.client.Post(f.url+"/process-inventory", "application/json", bytes.NewReader(body))
	if err != nil {
		f.log.Error("full_inventory forward failed", "err", err, "char", char)
		return
	}
	defer drain(resp)
	if resp.StatusCode >= 400 {
		f.log.Warn("inventory service error (full_inventory)", "status", resp.StatusCode, "char", char)
	}
}

// handleInventoryDelta forwards a single add/update/remove. Fire-and-forget.
func (f *invForwarder) handleInventoryDelta(data map[string]any) {
	go func() {
		char := toStr(data["character_name"])
		lock := f.charLock(char)
		lock.Lock()
		defer lock.Unlock()
		f.sem <- struct{}{}
		defer func() { <-f.sem }()

		out := data
		switch toStr(data["action"]) {
		case "remove":
			if itemID := data["item_id"]; itemID != nil {
				req, _ := http.NewRequest(http.MethodDelete,
					fmt.Sprintf("%s/inventory/%s/item/%v", f.url, url.PathEscape(char), itemID), nil)
				if resp, err := f.client.Do(req); err != nil {
					f.log.Warn("inventory delta remove failed", "err", err, "char", char)
				} else {
					if resp.StatusCode >= 400 {
						f.log.Warn("inventory service error (delta remove)", "status", resp.StatusCode, "char", char)
					}
					drain(resp)
				}
			}
		case "add", "update":
			if item := data["item"]; item != nil {
				b, _ := json.Marshal(item)
				resp, err := f.client.Post(fmt.Sprintf("%s/inventory/%s/item", f.url, url.PathEscape(char)),
					"application/json", bytes.NewReader(b))
				if err != nil {
					f.log.Warn("inventory delta add/update failed", "err", err, "char", char)
				} else {
					if resp.StatusCode < 400 {
						// Re-broadcast the enriched item the service returns.
						var r map[string]any
						if json.NewDecoder(resp.Body).Decode(&r) == nil {
							if enriched, ok := r["item"]; ok && enriched != nil {
								out = map[string]any{
									"type":           "inventory_delta",
									"action":         toStr(data["action"]),
									"character_name": char,
									"item":           enriched,
								}
							}
						}
					} else {
						f.log.Warn("inventory service error (delta add/update)", "status", resp.StatusCode, "char", char)
					}
					drain(resp)
				}
			}
		}
		if f.broadcast != nil {
			f.broadcast(out)
		}
	}()
}

func drain(resp *http.Response) {
	if resp != nil && resp.Body != nil {
		_, _ = io.Copy(io.Discard, resp.Body)
		_ = resp.Body.Close()
	}
}