package observation

import (
	"errors"
	"strings"
	"testing"
	"time"

	"github.com/tegwick/fluid-core/internal/contract"
)

func testPolicy() RedactionPolicy {
	return DefaultRedactionPolicy([]byte("a-stable-salt-of-sufficient-length"))
}

func TestPolicyRequiresASalt(t *testing.T) {
	if err := (RedactionPolicy{}).Validate(); !errors.Is(err, ErrNoSalt) {
		t.Errorf("an unsalted policy validated: %v", err)
	}
	if err := testPolicy().Validate(); err != nil {
		t.Errorf("a salted policy was rejected: %v", err)
	}
}

// TestPseudonymIsStableAndOpaque covers both halves of the requirement: the
// same consumer must look the same over time, and the value must not give the
// identity back.
func TestPseudonymIsStableAndOpaque(t *testing.T) {
	p := testPolicy()

	first := p.Pseudonymize("bernd@example.com")
	if first == "" {
		t.Fatal("pseudonymizing a real identity produced nothing")
	}
	if strings.Contains(first, "bernd") || strings.Contains(first, "example.com") {
		t.Errorf("pseudonym leaks the identity: %q", first)
	}

	for i := 0; i < 20; i++ {
		if again := p.Pseudonymize("bernd@example.com"); again != first {
			t.Fatalf("pseudonym is unstable: %q then %q", first, again)
		}
	}

	if p.Pseudonymize("someone-else@example.com") == first {
		t.Error("two identities collided")
	}

	// A different salt must produce a different value, or the mapping would be
	// portable between deployments.
	other := DefaultRedactionPolicy([]byte("a-completely-different-salt-value"))
	if other.Pseudonymize("bernd@example.com") == first {
		t.Error("pseudonym does not depend on the salt")
	}

	if p.Pseudonymize("") != "" {
		t.Error("an empty identity should stay empty rather than become a pseudonym")
	}
}

func TestCleanRouteRedactsCredentialsButKeepsShape(t *testing.T) {
	p := testPolicy()

	got, redacted := p.CleanRoute("/v1/entries?token=hunter2&limit=10")
	if !redacted {
		t.Fatal("a route carrying a token was not flagged as redacted")
	}
	if strings.Contains(got, "hunter2") {
		t.Errorf("token survived redaction: %q", got)
	}
	// Which parameters were sent is interface evidence in itself.
	if !strings.Contains(got, "token=") {
		t.Errorf("the parameter name was dropped, losing the evidence: %q", got)
	}
	if !strings.Contains(got, "limit=10") {
		t.Errorf("a harmless parameter was removed: %q", got)
	}

	plain, redacted := p.CleanRoute("/v1/entries")
	if redacted || plain != "/v1/entries" {
		t.Errorf("a clean route was altered: %q", plain)
	}
}

func TestUnparseableQueryIsDroppedEntirely(t *testing.T) {
	p := testPolicy()
	// A query that cannot be inspected cannot be shown to be safe.
	got, redacted := p.CleanRoute("/v1/entries?%zz")
	if !redacted {
		t.Error("an unparseable query was not flagged")
	}
	if strings.Contains(got, "%zz") {
		t.Errorf("unparseable query survived: %q", got)
	}
}

func TestScrubRemovesSensitivePatterns(t *testing.T) {
	p := testPolicy()

	for _, tc := range []struct{ name, in, mustNotContain string }{
		{"bearer token", "upstream rejected: Bearer eyJhbGciOiJIUzI1NiJ9.abc", "eyJhbGciOiJIUzI1NiJ9"},
		{"email", "no account for bernd@example.com", "bernd@example.com"},
		{"connection string", "dial postgres://user:hunter2@db.internal/prod", "hunter2"},
	} {
		got, hit := p.Scrub(tc.in)
		if !hit {
			t.Errorf("%s: not flagged as redacted", tc.name)
		}
		if strings.Contains(got, tc.mustNotContain) {
			t.Errorf("%s: sensitive value survived: %q", tc.name, got)
		}
	}

	if got, hit := p.Scrub("timeout after 5000ms"); hit || got != "timeout after 5000ms" {
		t.Errorf("harmless text was altered: %q", got)
	}
}

// TestApplyRecordsWhatItDid: silent redaction would let an analyst mistake an
// absence of evidence for evidence of absence.
func TestApplyRecordsWhatItDid(t *testing.T) {
	p := testPolicy()

	ev := contract.FluidTelemetry{
		ConsumerRef: "bernd@example.com",
		Request:     &contract.FluidTelemetryRequest{Route: "/v1/entries?api_key=secret"},
		Error:       &contract.FluidTelemetryError{Class: contract.FluidTelemetryErrorClassBackendFailure, Detail: "dial postgres://u:p@db/x"},
	}
	p.Apply(&ev)

	if ev.Redaction == nil || !ev.Redaction.Applied {
		t.Fatal("redaction was applied but not recorded")
	}
	for _, want := range []string{"pseudonymize-consumer", "clean-route", "scrub-error-detail"} {
		found := false
		for _, r := range ev.Redaction.Rules {
			if r == want {
				found = true
			}
		}
		if !found {
			t.Errorf("rule %q not recorded; recorded: %v", want, ev.Redaction.Rules)
		}
	}
	if strings.Contains(ev.ConsumerRef, "@") {
		t.Error("consumer identity survived")
	}
}

func TestApplyIsIdempotent(t *testing.T) {
	// Events may pass through the filter more than once on their way to the
	// store; pseudonymizing a pseudonym would break consumer continuity.
	p := testPolicy()
	ev := contract.FluidTelemetry{ConsumerRef: "consumer-1"}

	p.Apply(&ev)
	once := ev.ConsumerRef
	p.Apply(&ev)

	if ev.ConsumerRef != once {
		t.Errorf("re-applying redaction changed the pseudonym: %q then %q", once, ev.ConsumerRef)
	}
}

func TestApplyOnCleanEventRecordsNoRedaction(t *testing.T) {
	p := testPolicy()
	ev := contract.FluidTelemetry{Request: &contract.FluidTelemetryRequest{Route: "/v1/entries"}}
	p.Apply(&ev)

	if ev.Redaction == nil {
		t.Fatal("redaction status not recorded at all")
	}
	if ev.Redaction.Applied {
		t.Errorf("a clean event was marked redacted: %v", ev.Redaction.Rules)
	}
}

func TestRetentionAndCohortFloor(t *testing.T) {
	p := testPolicy()
	now := time.Date(2026, 9, 4, 0, 0, 0, 0, time.UTC)

	old := contract.FluidTelemetry{OccurredAt: now.AddDate(0, 0, -91)}
	if !p.Expired(old, now) {
		t.Error("an event past retention was not expired")
	}
	recent := contract.FluidTelemetry{OccurredAt: now.AddDate(0, 0, -1)}
	if p.Expired(recent, now) {
		t.Error("a recent event was expired")
	}

	unbounded := p
	unbounded.RetentionDays = 0
	if unbounded.Expired(old, now) {
		t.Error("unbounded retention expired an event")
	}

	// A cohort of one is a named individual with extra steps.
	if !p.SuppressSmallCohort(1) {
		t.Error("a cohort of one was reportable")
	}
	if p.SuppressSmallCohort(50) {
		t.Error("a large cohort was suppressed")
	}
}