package routing

import (
	"sync"
	"testing"
)

func TestRuleSetUsesFirstMatchingRule(t *testing.T) {
	rules, err := Compile([]Rule{
		{Name: "specific", Match: Match{HostRegex: `(^|\.)jd\.com$`}, Upstreams: []string{"jd"}},
		{Name: "default", Match: Match{HostRegex: `.*`}, Action: ActionReject},
	})
	if err != nil {
		t.Fatalf("Compile(): %v", err)
	}

	got, ok := rules.Match(Request{Host: "api.jd.com", Method: "GET", Path: "/"})
	if !ok || got.Name != "specific" {
		t.Fatalf("Match() = %q, %v; want specific, true", got.Name, ok)
	}
}

func TestRuleSetIsDetachedFromInputAndReturnedRules(t *testing.T) {
	input := []Rule{{
		Name: "route-a",
		Match: Match{
			HostRegex: `.*`,
			Methods:   []string{"GET"},
			Headers:   map[string]string{"X-Tenant": "a"},
		},
		Upstreams: []string{"provider-a"},
	}}
	rules, err := Compile(input)
	if err != nil {
		t.Fatalf("Compile(): %v", err)
	}
	input[0].Match.Methods[0] = "POST"
	input[0].Match.Headers["X-Tenant"] = "changed"
	input[0].Upstreams[0] = "changed"

	matched, ok := rules.Match(Request{
		Host: "example.com", Method: "GET", Headers: map[string]string{"X-Tenant": "a"},
	})
	if !ok || matched.Upstreams[0] != "provider-a" {
		t.Fatalf("Match() after input mutation = %+v, %v", matched, ok)
	}
	matched.Match.Methods[0] = "DELETE"
	matched.Match.Headers["X-Tenant"] = "returned-change"
	matched.Upstreams[0] = "returned-change"
	second, ok := rules.Match(Request{
		Host: "example.com", Method: "GET", Headers: map[string]string{"X-Tenant": "a"},
	})
	if !ok || second.Upstreams[0] != "provider-a" || second.Match.Methods[0] != "GET" {
		t.Fatalf("Match() after returned-rule mutation = %+v, %v", second, ok)
	}
}

func TestSequentialSwitchesOnceAtThreshold(t *testing.T) {
	sequence, err := NewSequential([]string{"a", "b", "c"}, 5)
	if err != nil {
		t.Fatalf("NewSequential(): %v", err)
	}
	for range 4 {
		sequence.ObserveEmpty("a")
	}
	if got := sequence.Current(); got != "a" {
		t.Fatalf("Current() = %q before threshold, want a", got)
	}

	var wg sync.WaitGroup
	for range 100 {
		wg.Add(1)
		go func() {
			defer wg.Done()
			sequence.ObserveEmpty("a")
		}()
	}
	wg.Wait()

	if got := sequence.Current(); got != "b" {
		t.Fatalf("Current() = %q after concurrent threshold, want b", got)
	}
}

func TestSequentialValidFetchResetsEmptyCount(t *testing.T) {
	sequence, _ := NewSequential([]string{"a", "b"}, 5)
	for range 4 {
		sequence.ObserveEmpty("a")
	}
	sequence.ObserveValid("a")
	for range 4 {
		sequence.ObserveEmpty("a")
	}
	if got := sequence.Current(); got != "a" {
		t.Fatalf("Current() = %q, want a after reset", got)
	}
}

func TestSequentialSharesUpstreamEmptyStateAcrossRoutingCursors(t *testing.T) {
	empty := NewUpstreamEmptyState()
	first, err := NewSequentialWithState([]string{"a", "b"}, 5, EndStayLast, empty)
	if err != nil {
		t.Fatalf("NewSequentialWithState(first): %v", err)
	}
	second, err := NewSequentialWithState([]string{"a", "c"}, 5, EndStayLast, empty)
	if err != nil {
		t.Fatalf("NewSequentialWithState(second): %v", err)
	}

	for range 5 {
		first.ObserveEmpty("a")
	}
	if got := first.Current(); got != "b" {
		t.Fatalf("first.Current() = %q, want b", got)
	}
	if got := second.EmptyCount("a"); got != 5 {
		t.Fatalf("second.EmptyCount(a) = %d, want shared count 5", got)
	}
	if !second.ObserveEmpty("a") || second.Current() != "c" {
		t.Fatalf("second did not advance from shared empty state: current=%q", second.Current())
	}
}

func TestSequentialStopEndBehaviorHasNoCurrentSelection(t *testing.T) {
	sequence, err := NewSequentialWithState([]string{"a"}, 1, EndStop, NewUpstreamEmptyState())
	if err != nil {
		t.Fatalf("NewSequentialWithState(): %v", err)
	}
	if !sequence.ObserveEmpty("a") {
		t.Fatal("ObserveEmpty() = false, want transition to stopped")
	}
	if current, ok, version := sequence.CurrentSelection(); ok || current != "" || version != 2 {
		t.Fatalf("CurrentSelection() = %q, %v, %d; want stopped version 2", current, ok, version)
	}
}

func TestSequentialLoopDoesNotReuseSameEmptyEpisode(t *testing.T) {
	empty := NewUpstreamEmptyState()
	sequence, err := NewSequentialWithState([]string{"a", "b"}, 1, EndLoop, empty)
	if err != nil {
		t.Fatalf("NewSequentialWithState(): %v", err)
	}
	if !sequence.ObserveEmpty("a") || !sequence.ObserveEmpty("b") || sequence.Current() != "a" {
		t.Fatalf("sequence did not loop to a: current=%q", sequence.Current())
	}
	if sequence.ObserveEmpty("a") || sequence.Current() != "a" {
		t.Fatal("sequence reused the same a empty episode")
	}
	sequence.ObserveValid("a")
	if !sequence.ObserveEmpty("a") || sequence.Current() != "b" {
		t.Fatal("sequence did not advance after a new empty episode")
	}
}