package redis

import (
	"context"
	"strings"
	"sync"
	"testing"

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

// fakeScripter simulates enough of Scripter for unit testing Script behavior.
// It records which redis commands were invoked and can simulate NOSCRIPT.
type fakeScripter struct {
	mu sync.Mutex

	// call counters
	scriptLoadCalls int
	evalCalls       int
	evalShaCalls    int
	evalROCalls     int
	evalShaROCalls  int

	// behavior controls
	hashToReturn string

	// If set, the first EvalSha/EvalShaRO returns a NOSCRIPT error.
	failFirstEvalShaWithNoScr   bool
	failFirstEvalShaROWithNoScr bool
}

func (f *fakeScripter) ScriptLoad(ctx context.Context, script string) *StringCmd {
	f.mu.Lock()
	f.scriptLoadCalls++
	f.mu.Unlock()

	cmd := NewStringCmd(ctx)
	cmd.SetVal(f.hashToReturn)
	return cmd
}

func (f *fakeScripter) ScriptExists(ctx context.Context, hashes ...string) *BoolSliceCmd {
	cmd := NewBoolSliceCmd(ctx)
	vals := make([]bool, len(hashes))
	for i := range vals {
		vals[i] = true
	}
	cmd.SetVal(vals)
	return cmd
}

func (f *fakeScripter) Eval(ctx context.Context, script string, keys []string, args ...interface{}) *Cmd {
	f.mu.Lock()
	f.evalCalls++
	f.mu.Unlock()

	cmd := NewCmd(ctx)
	cmd.SetErr(nil)
	return cmd
}

func (f *fakeScripter) EvalSha(ctx context.Context, sha1 string, keys []string, args ...interface{}) *Cmd {
	f.mu.Lock()
	f.evalShaCalls++
	callNum := f.evalShaCalls
	fail := f.failFirstEvalShaWithNoScr && callNum == 1
	f.mu.Unlock()

	cmd := NewCmd(ctx)
	if fail {
		// Use RedisError so go-redis NOSCRIPT detection triggers.
		cmd.SetErr(proto.RedisError("NOSCRIPT No matching script. Please use EVAL."))
		return cmd
	}
	cmd.SetErr(nil)
	return cmd
}

func (f *fakeScripter) EvalRO(ctx context.Context, script string, keys []string, args ...interface{}) *Cmd {
	f.mu.Lock()
	f.evalROCalls++
	f.mu.Unlock()

	cmd := NewCmd(ctx)
	cmd.SetErr(nil)
	return cmd
}

func (f *fakeScripter) EvalShaRO(ctx context.Context, sha1 string, keys []string, args ...interface{}) *Cmd {
	f.mu.Lock()
	f.evalShaROCalls++
	callNum := f.evalShaROCalls
	fail := f.failFirstEvalShaROWithNoScr && callNum == 1
	f.mu.Unlock()

	cmd := NewCmd(ctx)
	if fail {
		cmd.SetErr(proto.RedisError("NOSCRIPT No matching script. Please use EVAL."))
		return cmd
	}
	cmd.SetErr(nil)
	return cmd
}

func TestNewScriptServerSHA_Run_UsesScriptLoadAndEvalSha_NoEval(t *testing.T) {
	ctx := context.Background()
	c := &fakeScripter{hashToReturn: strings.Repeat("a", 40)}

	s := NewScriptServerSHA("return 1")
	if err := s.Run(ctx, c, []string{"k"}).Err(); err != nil {
		t.Fatalf("Run() err: %v", err)
	}

	if c.scriptLoadCalls != 1 {
		t.Fatalf("expected ScriptLoad 1 call, got %d", c.scriptLoadCalls)
	}
	if c.evalShaCalls != 1 {
		t.Fatalf("expected EvalSha 1 call, got %d", c.evalShaCalls)
	}
	if c.evalCalls != 0 {
		t.Fatalf("expected Eval 0 calls, got %d", c.evalCalls)
	}
}

func TestNewScriptServerSHA_Run_RetriesOnNoScript_NoEvalFallback(t *testing.T) {
	ctx := context.Background()
	c := &fakeScripter{
		hashToReturn:              strings.Repeat("b", 40),
		failFirstEvalShaWithNoScr: true,
	}

	s := NewScriptServerSHA("return 1")
	if err := s.Run(ctx, c, []string{"k"}).Err(); err != nil {
		t.Fatalf("Run() err: %v", err)
	}

	// Expected:
	// - ScriptLoad once (hash cached in Script)
	// - EvalSha twice (first NOSCRIPT, second retry)
	if c.scriptLoadCalls != 1 {
		t.Fatalf("expected ScriptLoad 1 call (hash cached), got %d", c.scriptLoadCalls)
	}
	if c.evalShaCalls != 2 {
		t.Fatalf("expected EvalSha 2 calls (retry), got %d", c.evalShaCalls)
	}
	// Critical: serverSHA path should NOT fallback to Eval
	if c.evalCalls != 0 {
		t.Fatalf("expected Eval 0 calls, got %d", c.evalCalls)
	}
}

func TestNewScriptServerSHA_RunRO_UsesScriptLoadAndEvalShaRO_NoEvalRO(t *testing.T) {
	ctx := context.Background()
	c := &fakeScripter{hashToReturn: strings.Repeat("c", 40)}

	s := NewScriptServerSHA("return 1")
	if err := s.RunRO(ctx, c, []string{"k"}).Err(); err != nil {
		t.Fatalf("RunRO() err: %v", err)
	}

	if c.scriptLoadCalls != 1 {
		t.Fatalf("expected ScriptLoad 1 call, got %d", c.scriptLoadCalls)
	}
	if c.evalShaROCalls != 1 {
		t.Fatalf("expected EvalShaRO 1 call, got %d", c.evalShaROCalls)
	}
	if c.evalROCalls != 0 {
		t.Fatalf("expected EvalRO 0 calls, got %d", c.evalROCalls)
	}
}

func TestNewScriptServerSHA_RunRO_RetriesOnNoScript_NoEvalROFallback(t *testing.T) {
	ctx := context.Background()
	c := &fakeScripter{
		hashToReturn:                strings.Repeat("d", 40),
		failFirstEvalShaROWithNoScr: true,
	}

	s := NewScriptServerSHA("return 1")
	if err := s.RunRO(ctx, c, []string{"k"}).Err(); err != nil {
		t.Fatalf("RunRO() err: %v", err)
	}

	if c.scriptLoadCalls != 1 {
		t.Fatalf("expected ScriptLoad 1 call (hash cached), got %d", c.scriptLoadCalls)
	}
	if c.evalShaROCalls != 2 {
		t.Fatalf("expected EvalShaRO 2 calls (retry), got %d", c.evalShaROCalls)
	}
	if c.evalROCalls != 0 {
		t.Fatalf("expected EvalRO 0 calls, got %d", c.evalROCalls)
	}
}