package milergeo

import (
	"context"
	"errors"
	"strings"
	"testing"

	"github.com/redis/go-redis/v9"
)

// fakeRedis answers the three geo commands the way a given Redis would.
type fakeRedis struct {
	searchErr  error // GEOSEARCH result; nil = supported
	radiusErr  error
	addErr     error
	locs       []redis.GeoLocation
	searchHits int
	radiusHits int
	remErr     error
	removed    []interface{}
}

func (f *fakeRedis) ZRem(ctx context.Context, _ string, members ...interface{}) *redis.IntCmd {
	f.removed = append(f.removed, members...)
	cmd := redis.NewIntCmd(ctx)
	if f.remErr != nil {
		cmd.SetErr(f.remErr)
	} else {
		cmd.SetVal(int64(len(members)))
	}
	return cmd
}

func (f *fakeRedis) GeoSearchLocation(ctx context.Context, _ string, q *redis.GeoSearchLocationQuery) *redis.GeoSearchLocationCmd {
	f.searchHits++
	cmd := redis.NewGeoSearchLocationCmd(ctx, q)
	if f.searchErr != nil {
		cmd.SetErr(f.searchErr)
	} else {
		cmd.SetVal(f.locs)
	}
	return cmd
}

func (f *fakeRedis) GeoRadius(_ context.Context, _ string, _, _ float64, _ *redis.GeoRadiusQuery) *redis.GeoLocationCmd {
	f.radiusHits++
	return redis.NewGeoLocationCmdResult(f.locs, f.radiusErr)
}

func (f *fakeRedis) GeoAdd(ctx context.Context, _ string, _ ...*redis.GeoLocation) *redis.IntCmd {
	cmd := redis.NewIntCmd(ctx)
	if f.addErr != nil {
		cmd.SetErr(f.addErr)
	} else {
		cmd.SetVal(1)
	}
	return cmd
}

var nearby = []redis.GeoLocation{{Name: "38", Dist: 0.03}, {Name: "23", Dist: 0.4}}

func TestSearchUsesGeosearchOnRedis62(t *testing.T) {
	legacyOnly.Store(false)
	f := &fakeRedis{locs: nearby}
	got, err := Search(context.Background(), f, 11.0053, 76.9511, 10, 10)
	if err != nil || len(got) != 2 || got[0].Name != "38" {
		t.Fatalf("got %v, %v", got, err)
	}
	if f.searchHits != 1 || f.radiusHits != 0 {
		t.Fatalf("GEOSEARCH must be used when supported: search=%d radius=%d", f.searchHits, f.radiusHits)
	}
}

// The production failure: Redis < 6.2 has no GEOSEARCH, so every order found
// "no riders". The fallback must find them, and stop retrying GEOSEARCH.
func TestSearchFallsBackOnOldRedis(t *testing.T) {
	legacyOnly.Store(false)
	t.Cleanup(func() { legacyOnly.Store(false) })
	f := &fakeRedis{searchErr: errors.New("ERR unknown command 'GEOSEARCH', with args beginning with: 'milers:locations'"), locs: nearby}
	for i := 0; i < 3; i++ {
		got, err := Search(context.Background(), f, 11.0053, 76.9511, 10, 10)
		if err != nil || len(got) != 2 {
			t.Fatalf("call %d: got %v, %v", i, got, err)
		}
	}
	if f.searchHits != 1 || f.radiusHits != 3 {
		t.Fatalf("after the first rejection only GEORADIUS should run: search=%d radius=%d", f.searchHits, f.radiusHits)
	}
	if p := Probe(context.Background(), f); !strings.Contains(p, "GEORADIUS fallback") {
		t.Fatalf("probe = %q", p)
	}
}

// Any other failure must surface, not read as an empty street.
func TestSearchReturnsOtherErrors(t *testing.T) {
	legacyOnly.Store(false)
	f := &fakeRedis{searchErr: errors.New("WRONGTYPE Operation against a key holding the wrong kind of value")}
	if _, err := Search(context.Background(), f, 11, 76, 10, 10); err == nil || !strings.Contains(err.Error(), "WRONGTYPE") {
		t.Fatalf("want the WRONGTYPE error, got %v", err)
	}
	if f.radiusHits != 0 || legacyOnly.Load() {
		t.Fatal("a non-'unknown command' error must not switch to the fallback")
	}
	if p := Probe(context.Background(), f); !strings.HasPrefix(p, "error: ") {
		t.Fatalf("probe = %q", p)
	}
}

func TestIndexReportsWriteFailure(t *testing.T) {
	if err := Index(context.Background(), &fakeRedis{}, 38, 11.0, 76.9); err != nil {
		t.Fatalf("ok write: %v", err)
	}
	err := Index(context.Background(), &fakeRedis{addErr: errors.New("WRONGTYPE Operation")}, 38, 11.0, 76.9)
	if err == nil || !strings.Contains(err.Error(), "WRONGTYPE") {
		t.Fatalf("want the write error, got %v", err)
	}
}

// db.Rdb is a *redis.Client; before InitRedis it is a nil pointer, which in
// an interface is not == nil. It must be refused, not dereferenced.
func TestNilClientIsRefused(t *testing.T) {
	var rdb *redis.Client
	if _, err := Search(context.Background(), rdb, 11, 76, 10, 10); err == nil {
		t.Fatal("nil client must be an error")
	}
	if err := Index(context.Background(), rdb, 1, 11, 76); err == nil {
		t.Fatal("nil client must be an error")
	}
	if p := Probe(context.Background(), rdb); !strings.HasPrefix(p, "error") {
		t.Fatalf("probe = %q", p)
	}
}

// A GEO member never expires, and nothing removed one when a rider went off
// duty — so milers:locations kept every rider who had ever started a shift,
// frozen where they last reported. Assignment takes the N NEAREST members, so
// those stale entries crowded out riders who were actually working and the
// candidate pool collapsed to whoever survived the freshness filter.
func TestRemoveDropsTheRiderFromTheSet(t *testing.T) {
	f := &fakeRedis{}
	if err := Remove(context.Background(), f, 412); err != nil {
		t.Fatalf("Remove: %v", err)
	}
	if len(f.removed) != 1 || f.removed[0] != "412" {
		t.Errorf("removed = %v, want [\"412\"]", f.removed)
	}
}

// The member is the rider's userid as a DECIMAL STRING — the same spelling
// GeoAdd writes and Search reads back. A mismatch here would remove nothing
// and report success.
func TestRemoveUsesTheSameMemberSpellingAsAdd(t *testing.T) {
	f := &fakeRedis{}
	_ = Remove(context.Background(), f, 7)
	if f.removed[0] != "7" {
		t.Errorf("member = %v, want \"7\" (decimal string, not an int)", f.removed[0])
	}
}

// Best-effort at the call site: the rider is off duty either way, and the
// freshness check still excludes them. The error must reach the caller so it
// can be logged rather than swallowed here.
func TestRemoveReturnsTheError(t *testing.T) {
	f := &fakeRedis{remErr: errors.New("redis down")}
	if err := Remove(context.Background(), f, 1); err == nil {
		t.Error("Remove swallowed the error")
	}
}

func TestRemoveOnNilClientIsANoOp(t *testing.T) {
	if err := Remove(context.Background(), nil, 1); err != nil {
		t.Errorf("Remove(nil) = %v, want nil", err)
	}
}