package core

import (
	"fmt"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"llmsproxy/internal/config"
)

// AutoChainFor sits on the request hot path and reads keyAutoChains with no
// lock, while SaveKeyAuto / rebuildRegistry replace that map from the admin
// path. A "call it twice" test never interleaves those, so it would pass even
// if the map were mutated in place. These tests run both sides at once under
// -race and assert what readers actually observe.
//
// The property: a reader sees a chain that is either the key's own or the
// global one — never a torn or empty one. If rebuildKeyAutoChains built the
// map in place instead of swapping a fresh pointer, readers would sometimes
// see a partially-filled map and silently fall back to the global chain, i.e.
// a user quietly losing their configured chain under load.

// concurrentChainConfig builds N keys, half with their own chain pointing at a
// distinct model so a fallback to the global chain is distinguishable.
func concurrentChainConfig(t *testing.T, n int) *config.Config {
	t.Helper()
	cfg := perKeyTestConfig(t)
	cfg.Keys = nil
	cfg.GatewayKeys = []string{"sk-gw-admin"}
	cfg.Auto = []config.ModelScope{{Model: "gpt-4o", Source: "s1", Tier: 1}}
	for i := 0; i < n; i++ {
		k := config.GWKey{
			Key:  fmt.Sprintf("sk-gw-k%03d", i),
			Role: "user",
			Name: fmt.Sprintf("user%d", i),
		}
		if i%2 == 0 {
			k.Auto = []config.ModelScope{{Model: "gpt-4o-mini", Source: "s1", Tier: 1}}
		}
		cfg.Keys = append(cfg.Keys, k)
	}
	return cfg
}

func TestAutoChainForConcurrentWithSaveKeyAuto(t *testing.T) {
	cfg := concurrentChainConfig(t, 40)
	c := newTestCore(t, cfg)

	var stop atomic.Bool
	var wg sync.WaitGroup
	var bad atomic.Int64

	for r := 0; r < 8; r++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for !stop.Load() {
				for i := 0; i < 40; i++ {
					key := fmt.Sprintf("sk-gw-k%03d", i)
					ch, ok := c.AutoChainFor(key)
					if !ok || ch == nil || len(ch.Tiers) == 0 {
						bad.Add(1)
						continue
					}
					// Legal values are this key's own chain model (either
					// side of the writer's flip) or the global chain's. The
					// assertion is about the legal set, not a fixed value:
					// the writers legitimately change the chain underneath.
					got := ch.Tiers[0].Slots[0].Model
					if got != "gpt-4o" && got != "gpt-4o-mini" {
						bad.Add(1)
					}
				}
			}
		}()
	}

	for w := 0; w < 2; w++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			model := "gpt-4o-mini"
			for i := 0; i < 25 && !stop.Load(); i++ {
				for j := 0; j < 40; j += 2 {
					if err := c.SaveKeyAuto(fmt.Sprintf("sk-gw-k%03d", j), []config.ModelScope{
						{Model: model, Source: "s1", Tier: 1},
					}); err != nil {
						bad.Add(1)
						return
					}
				}
				if model == "gpt-4o-mini" {
					model = "gpt-4o"
				} else {
					model = "gpt-4o-mini"
				}
			}
		}()
	}

	time.Sleep(400 * time.Millisecond)
	stop.Store(true)
	wg.Wait()

	if n := bad.Load(); n > 0 {
		t.Fatalf("%d reads saw a chain outside {own, global} — the cache is "+
			"being swapped in place instead of atomically", n)
	}
}

// The registry rebuild path (AddSource / RemoveSource) also replaces the
// cache, so readers must keep a usable chain throughout.
//
// Churned sources use a "churn" prefix on purpose: deleting a source a chain
// references legitimately empties that chain (BuildChain drops unresolvable
// slots), and asserting otherwise would be testing a fiction rather than the
// code.
func TestAutoChainForConcurrentWithSourceChanges(t *testing.T) {
	cfg := concurrentChainConfig(t, 20)
	c := newTestCore(t, cfg)

	var stop atomic.Bool
	var wg sync.WaitGroup
	var bad atomic.Int64

	for r := 0; r < 6; r++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			for !stop.Load() {
				for i := 0; i < 20; i++ {
					ch, ok := c.AutoChainFor(fmt.Sprintf("sk-gw-k%03d", i))
					if !ok || ch == nil || len(ch.Tiers) == 0 {
						bad.Add(1)
						continue
					}
					if got := ch.Tiers[0].Slots[0].Model; got != "gpt-4o" && got != "gpt-4o-mini" {
						bad.Add(1)
					}
				}
			}
		}()
	}

	wg.Add(1)
	go func() {
		defer wg.Done()
		for n := 0; n < 30 && !stop.Load(); n++ {
			name := fmt.Sprintf("churn%d", n)
			_ = c.AddSource(config.Source{
				Name: name, BaseURL: "http://127.0.0.1:9/v1", Adapter: "openai",
				Models: []config.Model{{ID: "m-" + name, Priority: 10}}},
			)
			_ = c.RemoveSource(name)
		}
	}()

	time.Sleep(500 * time.Millisecond)
	stop.Store(true)
	wg.Wait()

	if n := bad.Load(); n > 0 {
		t.Fatalf("%d reads lost the chain while unrelated sources were churned", n)
	}
}

// Many distinct keys: the lookup must stay a map hit and must not degrade into
// returning the global chain as the key count grows.
func TestAutoChainForManyKeys(t *testing.T) {
	cfg := concurrentChainConfig(t, 500)
	c := newTestCore(t, cfg)

	for i := 0; i < 500; i++ {
		key := fmt.Sprintf("sk-gw-k%03d", i)
		ch, _ := c.AutoChainFor(key)
		if ch == nil || len(ch.Tiers) == 0 {
			t.Fatalf("key %s lost its chain with 500 keys configured", key)
		}
		want := "gpt-4o"
		if i%2 == 0 {
			want = "gpt-4o-mini"
		}
		if got := ch.Tiers[0].Slots[0].Model; got != want {
			t.Fatalf("key %s got %q, want %q", key, got, want)
		}
	}
}