package hashcash_test

import (
	"crypto/sha256"
	"encoding/hex"
	"testing"

	"git.eeqj.de/sneak/neoirc/internal/hashcash"
)

const (
	testChannel  = "#general"
	testBodyText = `["hello world"]`
)

func testBodyHash() string {
	hash := sha256.Sum256([]byte(testBodyText))

	return hex.EncodeToString(hash[:])
}

func TestChannelValidateHappyPath(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	stamp := hashcash.MintChannelStamp(
		testBits, testChannel, bodyHash,
	)

	err := validator.ValidateStamp(
		stamp, testBits, testChannel, bodyHash,
	)
	if err != nil {
		t.Fatalf("valid channel stamp rejected: %v", err)
	}
}

func TestChannelValidateWrongChannel(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	stamp := hashcash.MintChannelStamp(
		testBits, testChannel, bodyHash,
	)

	err := validator.ValidateStamp(
		stamp, testBits, "#other", bodyHash,
	)
	if err == nil {
		t.Fatal("expected channel mismatch error")
	}
}

func TestChannelValidateWrongBodyHash(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	stamp := hashcash.MintChannelStamp(
		testBits, testChannel, bodyHash,
	)

	wrongHash := sha256.Sum256([]byte("different body"))
	wrongBodyHash := hex.EncodeToString(wrongHash[:])

	err := validator.ValidateStamp(
		stamp, testBits, testChannel, wrongBodyHash,
	)
	if err == nil {
		t.Fatal("expected body hash mismatch error")
	}
}

func TestChannelValidateInsufficientBits(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	// Mint with 2 bits but require 4.
	stamp := hashcash.MintChannelStamp(
		testBits, testChannel, bodyHash,
	)

	err := validator.ValidateStamp(
		stamp, 4, testChannel, bodyHash,
	)
	if err == nil {
		t.Fatal("expected insufficient bits error")
	}
}

func TestChannelValidateZeroBitsSkips(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()

	err := validator.ValidateStamp(
		"garbage", 0, "#ch", "abc",
	)
	if err != nil {
		t.Fatalf("zero bits should skip: %v", err)
	}
}

func TestChannelValidateBadFormat(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()

	err := validator.ValidateStamp(
		"not:valid", testBits, testChannel, "abc",
	)
	if err == nil {
		t.Fatal("expected bad format error")
	}
}

func TestChannelValidateBadVersion(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	stamp := "2:2:260317:#general:" + bodyHash + ":counter"

	err := validator.ValidateStamp(
		stamp, testBits, testChannel, bodyHash,
	)
	if err == nil {
		t.Fatal("expected bad version error")
	}
}

func TestChannelValidateExpiredStamp(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	// Mint with a very old date by manually constructing.
	stamp := mintStampWithDate(
		t, testBits, testChannel, "200101",
	)

	err := validator.ValidateStamp(
		stamp, testBits, testChannel, bodyHash,
	)
	if err == nil {
		t.Fatal("expected expired stamp error")
	}
}

func TestChannelValidateMissingBodyHash(t *testing.T) {
	t.Parallel()

	validator := hashcash.NewChannelValidator()
	bodyHash := testBodyHash()

	// Construct a stamp with empty body hash field.
	stamp := mintStampWithDate(
		t, testBits, testChannel, todayDate(),
	)

	// This uses the session-style stamp which has empty
	// ext field — body hash is missing.
	err := validator.ValidateStamp(
		stamp, testBits, testChannel, bodyHash,
	)
	if err == nil {
		t.Fatal("expected missing body hash error")
	}
}

func TestBodyHash(t *testing.T) {
	t.Parallel()

	body := []byte(`["hello world"]`)
	bodyHash := hashcash.BodyHash(body)

	if len(bodyHash) != 64 {
		t.Fatalf(
			"expected 64-char hex hash, got %d",
			len(bodyHash),
		)
	}

	// Same input should produce same hash.
	bodyHash2 := hashcash.BodyHash(body)
	if bodyHash != bodyHash2 {
		t.Fatal("body hash not deterministic")
	}

	// Different input should produce different hash.
	bodyHash3 := hashcash.BodyHash([]byte("different"))
	if bodyHash == bodyHash3 {
		t.Fatal("different inputs produced same hash")
	}
}

func TestStampHash(t *testing.T) {
	t.Parallel()

	hash1 := hashcash.StampHash("stamp1")
	hash2 := hashcash.StampHash("stamp2")

	if hash1 == hash2 {
		t.Fatal("different stamps produced same hash")
	}

	// Same input should be deterministic.
	hash1b := hashcash.StampHash("stamp1")
	if hash1 != hash1b {
		t.Fatal("stamp hash not deterministic")
	}
}

func TestMintChannelStamp(t *testing.T) {
	t.Parallel()

	bodyHash := testBodyHash()
	stamp := hashcash.MintChannelStamp(
		testBits, testChannel, bodyHash,
	)

	if stamp == "" {
		t.Fatal("expected non-empty stamp")
	}

	// Validate the minted stamp.
	validator := hashcash.NewChannelValidator()

	err := validator.ValidateStamp(
		stamp, testBits, testChannel, bodyHash,
	)
	if err != nil {
		t.Fatalf("minted stamp failed validation: %v", err)
	}
}