package gobang

import (
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"slices"
	"strings"
	"time"

	"guuid"
)



func test_SetOf() {
	TestStart("SetOf()")

	Testing("empty set", func() {
		expected := SetT[int]{
			data: map[int]struct{}{
			},
		}

		TAssertEqual(SetOf[int](), expected)
	})

	Testing("equal sets", func() {
		expected := SetT[int]{
			data: map[int]struct{}{
				1: struct{}{},
				2: struct{}{},
				3: struct{}{},
			},
		}

		TAssertEqual(SetOf(1, 2, 3), expected)
	})
}

func test_Contains() {
	TestStart("Contains()")

	Testing("trivial example usage", func() {
		s := SetOf(1, 2, 3, 4, 5)
		TAssertEqual(Contains(s, 0), false)
		TAssertEqual(Contains(s, 1), true)
		TAssertEqual(Contains(s, 5), true)
		TAssertEqual(Contains(s, 6), false)
	})
}

func test_MapIndexed() {
	TestStart("MapIndexed()")

	Testing("empty array", func() {
		noop := func(s string, i int) string {
			return s
		}

		arr := []string{}
		TAssertEqual(MapIndexed(noop, arr), arr)
	})

	Testing("replace content with index", func() {
		index := func(s string, i int) int {
			return i
		}

		TAssertEqual(
			MapIndexed(index, []string{"a", "b", "c"}),
			[]int{0, 1, 2},
		)
	})

	Testing("a computed value", func() {
		fn := func(x int, i int) int {
			return x + i
		}

		TAssertEqual(
			MapIndexed(fn, []int{1, 2, 3, 4, 5}),
			[]int{1, 3, 5, 7, 9},
		)
	})
}

func test_Map() {
	TestStart("Map()")

	Testing("empty array", func() {
		noop := func(s string) string {
			return s
		}

		arr := []string{}
		TAssertEqual(Map(noop, arr), arr)
	})

	Testing("a derived value", func() {
		appendBang := func(s string) string {
			return s + "!"
		}

		TAssertEqual(
			Map(appendBang, []string{"a", "b", "c"}),
			[]string{"a!", "b!", "c!"},
		)
	})
}

func test_Filter() {
	TestStart("Filter()")

	fn := func(i int) bool {
		return i < 10
	}


	Testing("empty array", func() {
		arr := []int{}
		TAssertEqual(Filter(fn, arr), arr)
	})

	Testing("filters everything", func() {
		arr := []int{10, 11, 12, 13, 14, 15}
		TAssertEqual(Filter(fn, arr), []int{})
	})

	Testing("filters nothing", func() {
		arr := []int{1, 2, 3, 4, 5}
		TAssertEqual(Filter(fn, arr), arr)
	})

	Testing("filters some", func() {
		TAssertEqual(
			Filter(fn, []int{8, 9, 10, 11, 12, 0, 13}),
			[]int{8, 9, 0},
		)
	})
}

func test_PanicIf() {
	TestStart("PanicIf()")

	myErr := errors.New("test error")


	Testing("noop when error is nil", func() {
		var err error
		PanicIf(err)
		PanicIf(nil)
	})

	Testing("panic when we have an error", func() {
		defer func() {
			TAssertEqual(recover(), myErr)
		}()
		PanicIf(myErr)
		TErrorNil(nil)
	})
}

func test_Must() {
	TestStart("Must()")

	myErr := errors.New("test error")
	f := func(shouldError bool) (string, error) {
		if shouldError {
			return "UNSEEN", myErr
		}

		return "no error", nil
	}


	Testing("value when error is nil", func() {
		TAssertEqual(Must(f(false)), "no error")
	})

	Testing("panic when we have an error", func() {
		defer func() {
			TAssertEqual(recover(), myErr)
		}()
		Must(f(true))
		TErrorNil(nil)
	})
}

func test_Clamp() {
	TestStart("Clamp()")

	Testing("equal values", func() {
		TAssertEqual(Clamp(0, 0, 0), 0)
		TAssertEqual(Clamp(1, 1, 1), 1)
		TAssertEqual(Clamp(1.0, 1.0, 1.0), 1.0)
	})

	Testing("within range", func() {
		TAssertEqual(Clamp(5, 0, 10), 5)
		TAssertEqual(Clamp(1.1, 1.0, 1.2), 1.1)
		TAssertEqual(Clamp(0, 0, 10), 0)
		TAssertEqual(Clamp(10, 0, 10), 10)
	})

	Testing("lower than min", func() {
		TAssertEqual(Clamp(1, 2, 3), 2)
		TAssertEqual(Clamp(1.0, 1.1, 1.2), 1.1)
	})

	Testing("greater than max", func() {
		TAssertEqual(Clamp(1, 11, 10), 10)
		TAssertEqual(Clamp(1.2, 1.0, 1.1), 1.1)
	})
}

func test_ValidateSQLTablePrefix() {
	TestStart("ValidateSQLTablePrefix()")

	Testing("simple identifiers are good", func() {
		input := []string{
			"simple",
			"id",
			"g00d",
			"VERY_GOOD",
		}

		for _, given := range input {
			TAssertEqual(ValidateSQLTablePrefix(given), nil)
		}
	})

	Testing("nothing fancy is allowed", func() {
		input := []string{
			"a-table",
			"0t",
			"",
			"thing\"",
			"*symbol",
			"symbol*",
		}

		for _, given := range input {
			TAssertEqual(
				ValidateSQLTablePrefix(given),
				ErrBadSQLTablePrefix,
			)
		}
	})
}

func test_WrapErrors() {
	TestStart("WrapErrors()")

	Testing("nil for empty args", func() {
		TAssertEqual(WrapErrors(), nil)
	})

	Testing("nil when all args are nil", func() {
		TAssertEqual(WrapErrors(nil, nil, nil), nil)
	})

	Testing("if only 1 is an error, return it", func() {
		err := errors.New("my error")
		TAssertEqual(WrapErrors(nil, nil, err), err)
	})

	Testing("otherwise wrap them, from right to left", func() {
		err1 := errors.New("error 1")
		err2 := errors.New("error 2")
		expected1 := fmt.Errorf("error %w on top of %w", err1, err2)
		expected2 := fmt.Errorf("error %w on top of %w", err2, err1)
		TAssertEqual(WrapErrors(nil, err1, nil, err2), expected1)
		TAssertEqual(WrapErrors(err2, nil, nil, err1), expected2)
	})
}

func test_SomeError() {
	TestStart("SomeError()")

	Testing("an empty array is nil", func() {
		TAssertEqual(SomeError(), nil)
	})

	Testing("only nil values is nil", func() {
		TAssertEqual(SomeError(nil, nil, nil), nil)
	})

	Testing("we get the first non-nil value", func() {
		err1 := errors.New("error 1")
		err2 := errors.New("error 2")
		TAssertEqual(SomeError(nil, err1, err2), err1)
	})
}

func test_SomeFnError() {
	TestStart("SomeFnError()")

	Testing("an empty arrays is also nil", func() {
		TAssertEqual(SomeFnError(), nil)
	})

	Testing("all functions are called", func() {
		i := 0
		fn := func() error {
			i++
			return nil
		}
		TAssertEqual(SomeFnError(fn, fn, fn), nil)
		TAssertEqual(i, 3)
	})

	Testing("we call all functions even if we get an error", func() {
		i := 0
		errs := []error{
			nil,
			nil,
			errors.New("fn error 2"),
			errors.New("fn error 3"),
			nil,
		}
		fn := func() error {
			i++
			return errs[i]
		}
		TAssertEqual(SomeFnError(fn, fn, fn, fn), errs[2])
		TAssertEqual(i, 4)
	})

	Testing("no error if some function is nil", func() {
		myErr := errors.New("the expected result")
		TAssertEqual(SomeFnError(
			func() error { return nil   },
			nil,
			func() error { return nil   },
			func() error { return myErr },
			func() error { return nil   },
		), myErr)
	})
}

func test_Random() {
	TestStart("Random()")

	Testing("we get the desired output size", func() {
		for i := 0; i < 100; i++ {
			buffer, err := Random(i)
			TErrorIf(err)
			TAssertEqual(len(buffer), i)
		}
	})

	Testing("error on bad randomReader value", func() {
		savedReader := randomReader
		randomReader = strings.NewReader("abc")

		rand1, err1 := Random(3)
		rand2, err2 := Random(3)
		TErrorIf(err1)
		TErrorNil(err2)
		TAssertEqual(rand1, []byte{ 0x61, 0x62, 0x63 })
		TAssertEqual(rand2, []byte(nil))

		randomReader = savedReader
	})
}

func test_sourceInfo() {
	TestStart("sourceInfo()")

	Testing("sourceInfo() is defined at...", func() {
		const FILENAME = "src/gobang.go"
		info := sourceInfo(1)
		TAssertEqual(info.Key, "src")
		TAssertEqual(len(info.Value.Group()), 3)

		TAssertEqual(info.Value.Group()[0].Key, "file")
		file := info.Value.Group()[0].Value.String()
		TAssertEqual(file[len(file) - len(FILENAME):], FILENAME)

		TAssertEqual(info.Value.Group()[1].Key, "function")
		TAssertEqual(
			info.Value.Group()[1].Value.String(),
			"gobang.sourceInfo",
		)

		TAssertEqual(info.Value.Group()[2].Key, "line")
		TAssertEqual(info.Value.Group()[2].Value.Kind(), slog.KindInt64)
	})

	Testing("we're calling it from...", func() {
		const FILENAME = "tests/gobang.go"
		info := sourceInfo(2)
		TAssertEqual(info.Key, "src")
		TAssertEqual(len(info.Value.Group()), 3)

		TAssertEqual(info.Value.Group()[0].Key, "file")
		file := info.Value.Group()[0].Value.String()
		TAssertEqual(file[len(file) - len(FILENAME):], FILENAME)

		TAssertEqual(info.Value.Group()[1].Key, "function")
		TAssertEqual(
			info.Value.Group()[1].Value.String(),
			"gobang.test_sourceInfo.func2",
		)

		TAssertEqual(info.Value.Group()[2].Key, "line")
		TAssertEqual(info.Value.Group()[2].Value.Kind(), slog.KindInt64)
	})
}

func test_logArgs() {
	TestStart("logArgs()")

	Testing("direct string array return", func() {
		args := logArgs("the-type")
		TAssertEqual(len(args), 6)
		TAssertEqual(args[0], "id")

		_, err := guuid.FromString(args[1])
		TErrorIf(err)

		expected := []string { "kind", "log", "type", "the-type" }
		TAssertEqual(args[2:], expected)
	})
}

func test_anyArr() {
	TestStart("anyArr()")

	Testing("we can turn []string into []any", func() {
		var input []string = []string { "one", "two", "three" }
		var given []any    = anyArr(input)
		var expected []any = []any { "one", "two", "three" }

		TAssertEqual(given, expected)
	})
}

func testLog(
	levelName string,
	filterLevel LogLevel,
	fn func(string, string, ...any),
) {
	savedLogger := slog.Default()
	savedLevel  := level

	s := new(strings.Builder)
	SetLoggerOutput(s)
	level = filterLevel

	fn("a-message", "a-type", "a-key", "a-value")

	{
		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		_, err = time.Parse(time.RFC3339, data["time"].(string))
		TErrorIf(err)

		TAssertEqual(data["level"].(string), levelName)
		TAssertEqual(data["kind" ].(string), "log")
		TAssertEqual(data["msg"  ].(string), "a-message")
		TAssertEqual(data["type" ].(string), "a-type")
		TAssertEqual(data["a-key"].(string), "a-value")
	}

	slog.SetDefault(savedLogger)
	level = savedLevel
}

func testNoLog(filterLevel LogLevel, fn func(string, string, ...any)) {
	savedLogger := slog.Default()
	savedLevel  := level

	s := new(strings.Builder)
	SetLoggerOutput(s)
	level = filterLevel
	fn("a-message", "a-type", "a-key", "a-value")

	TAssertEqual(s.String(), "")

	slog.SetDefault(savedLogger)
	level = savedLevel
}

func test_Debug() {
	TestStart("Debug()")

	Testing("exists in LevelDebug", func() {
		testLog("DEBUG", LevelDebug, Debug)
	})

	Testing("doesn't in lower levels", func() {
		testNoLog(LevelInfo, Debug)
	})
}

func test_Info() {
	TestStart("Info()")

	Testing("exists in LevelInfo", func() {
		testLog("INFO", LevelInfo, Info)
	})

	Testing("doesn't in lower levels", func() {
		testNoLog(LevelWarning, Info)
	})
}

func test_Warning() {
	TestStart("Warning()")

	Testing("exists in LevelWarning", func() {
		testLog("WARN" /* WARNING */, LevelWarning, Warning)
	})

	Testing("doesn't in lower levels", func() {
		testNoLog(LevelError, Warning)
	})
}

func test_Error() {
	TestStart("Error()")

	Testing("exists in LevelError", func() {
		testLog("ERROR", LevelError, Error)
	})

	Testing("doesn't in lower levels", func() {
		testNoLog(LevelNone, Error)
	})
}

func test_metric() {
	TestStart("metric()")

	Testing("noop when emitMetric is false", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = false

		metric("", "")
		TAssertEqual(s.String(), "")

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})

	Testing("JSON entry of kind \"metric\"", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = true

		metric("a-type", "a-label", "count-something", 123)

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		timeStr := data["time"].(string)
		_, err = time.Parse(time.RFC3339, timeStr)
		TErrorIf(err)

		_, err = guuid.FromString(data["id"].(string))
		TErrorIf(err)

		TAssertEqual(data["level"].(string), "INFO")
		TAssertEqual(data["msg"  ].(string), "_")
		TAssertEqual(data["kind" ].(string), "metric")
		TAssertEqual(data["type" ].(string), "a-type")
		TAssertEqual(data["label"].(string), "a-label")
		TAssertEqual(int(data["count-something"].(float64)), 123)

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})
}

func test_Timed() {
	TestStart("Timed()")

	Testing("we can use a noop thunk", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = true

		Timed("timer-label", func() {}, "key-1", "value-1")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		TAssertEqual(data["type"].(string),  "timer")
		TAssertEqual(data["label"].(string), "timer-label")
		TAssertEqual(data["key-1"].(string), "value-1")

		var ok bool
		_, ok = data["start"].(string)
		TAssertEqual(ok, true)
		_, ok = data["end"].(string)
		TAssertEqual(ok, true)
		_, ok = data["duration"].(float64)
		TAssertEqual(ok, true)

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})
}

func test_MakeCounter() {
	TestStart("MakeCounter()")

	Testing("\"value\" is always 1", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = true

		emitTCPError := MakeCounter("emit-tcp-error")
		emitTCPError("more-data", 555)

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		TAssertEqual(data["type" ].(string), "counter")
		TAssertEqual(data["label"].(string), "emit-tcp-error")
		TAssertEqual(int(data["value"    ].(float64)), 1)
		TAssertEqual(int(data["more-data"].(float64)), 555)

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})

	Testing("we have static and dynamic args", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = true

		emitTCPError := MakeCounter("label-1", "key-1", "value-1")
		emitTCPError("key-2", "value-2")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		TAssertEqual(data["type"].(string),  "counter")
		TAssertEqual(data["label"].(string), "label-1")
		TAssertEqual(data["key-1"].(string), "value-1")
		TAssertEqual(data["key-2"].(string), "value-2")

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})
}

func test_MakeGauge() {
	TestStart("MakeGauge()")

	Testing("errors on underflow", func() {
		savedLogger := slog.Default()
		savedLevel  := level

		s := new(strings.Builder)
		SetLoggerOutput(s)
		level = LevelError

		activeTCPConnections := MakeGauge("active-tcp-connections")
		activeTCPConnections.Dec()

		{
			var data map[string]interface{}
			err := json.Unmarshal([]byte(s.String()), &data)
			TErrorIf(err)

			TAssertEqual(data["level"].(string), "ERROR")
			TAssertEqual(
				data["msg"  ].(string),
				"Gauge went negative",
			)
			TAssertEqual(data["kind" ].(string), "log")
			TAssertEqual(data["type" ].(string), "process-metric")
			TAssertEqual(int(data["value"].(float64)), -1)
		}

		slog.SetDefault(savedLogger)
		level = savedLevel
	})

	Testing("\"value\" grows monotonically", func() {
		savedLogger := slog.Default()
		savedFlag   := emitMetric

		s := new(strings.Builder)
		SetLoggerOutput(s)
		emitMetric = true

		activeTCPConnections := MakeGauge("active-tcp-connections")
		activeTCPConnections.Inc()
		activeTCPConnections.Inc()
		activeTCPConnections.Dec()
		activeTCPConnections.Inc()
		activeTCPConnections.Inc("more-data", 999)

		strs := strings.Split(s.String(), "\n")
		TAssertEqual(len(strs), 6)
		TAssertEqual(strs[5], "")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(strs[len(strs) - 2]), &data)
		TErrorIf(err)

		TAssertEqual(data["type" ].(string), "gauge")
		TAssertEqual(data["label"].(string), "active-tcp-connections")
		TAssertEqual(int(data["value"    ].(float64)), 3)
		TAssertEqual(int(data["more-data"].(float64)), 999)

		slog.SetDefault(savedLogger)
		emitMetric = savedFlag
	})
}

func test_showColour() {
	TestStart("showColour()")

	const NAME = "NO_COLOUR"
	savedEnvvar := os.Getenv(NAME)
	defer os.Setenv(NAME, savedEnvvar)


	Testing("true when envvar is unset", func() {
		TErrorIf(os.Unsetenv(NAME))
		TAssertEqual(showColour(), true)
	})

	Testing("true when envvar is empty", func() {
		TErrorIf(os.Setenv(NAME, ""))
		TAssertEqual(showColour(), true)
	})

	Testing("false otherwise", func() {
		TErrorIf(os.Setenv(NAME, "1"))
		TAssertEqual(showColour(), false)
	})

}

func test_TestStart() {
	TestStart("TestStart()")

	Testing("simply writes the given name to `testOutput`", func() {
		w := new(strings.Builder)
		savedOutput := testOutput
		testOutput = w

		TestStart("theFunctionName()")
		TestStart("typeT.Method()")
		TestStart("variable")
		testOutput = savedOutput

		const expected =
			"theFunctionName():\n" +
			"typeT.Method():\n" +
			"variable:\n"

		TAssertEqual(w.String(), expected)
	})
}

func withSavedColour() func() {
	const NAME = "NO_COLOUR"
	savedEnvvar := os.Getenv(NAME)
	return func() {
		os.Setenv(NAME, savedEnvvar)
	}
}

func test_Testing() {
	TestStart("Testing()")

	Testing("tries to write a successful report of the test", func() {
		defer withSavedColour()()

		w := new(strings.Builder)
		savedOutput := testOutput
		testOutput = w


		TErrorIf(os.Unsetenv("NO_COLOUR"))
		Testing("colored description goes here", func() {})
		TErrorIf(os.Setenv("NO_COLOUR", "true"))
		Testing("uncolored description goes here", func() {})
		testOutput = savedOutput

		const expected =
			"\033[0;33mtesting\033[0m: " +
			"colored description goes here... " +
			"\033[0;32mOK\033[0m.\n" +
			"testing: uncolored description goes here... OK.\n"
		TAssertEqual(w.String(), expected)
	})
}

func test_terr() {
	TestStart("terr()")

	Testing("emits a failure string report", func() {
		defer withSavedColour()()

		w1 := new(strings.Builder)
		w2 := new(strings.Builder)
		savedOutput := testOutput

		TErrorIf(os.Unsetenv("NO_COLOUR"))
		testOutput = w1
		terr()
		TErrorIf(os.Setenv("NO_COLOUR", "1"))
		testOutput = w2
		terr()
		testOutput = savedOutput

		const expected1 = "\033[0;31mERR\033[0m ("
		const expected2 = "ERR ("
		const suffix = ").\n"
		TAssertEqual(strings.HasPrefix(w1.String(), expected1), true)
		TAssertEqual(strings.HasPrefix(w2.String(), expected2), true)
		TAssertEqual(strings.HasSuffix(w1.String(), suffix), true)
		TAssertEqual(strings.HasSuffix(w2.String(), suffix), true)
	})
}

func test_TAssertEqual() {
	TestStart("TAssertEqual()")

	Testing("noop on equal things", func() {
		TAssertEqual(1, 1)
		TAssertEqual("s", "s")
		TAssertEqual([]byte{ 0x12 }, []byte{ 0x12 })
	})

	Testing("fail on unequal", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TAssertEqual([]byte(nil), nil)

		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1:]

		TAssertEqual(n, 100)
		TAssertEqual(given, []string{
			"given != expected",
			"given:    []byte(nil)",
			"expected: <nil>",
			"",
		})
	})
}

func test_TAssertEqualS() {
	TestStart("TAssertEqualS()")

	Testing("noop for equal things", func() {
		TAssertEqualS(true, true, "ignored")
	})

	Testing("fail with message on unequal", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TAssertEqualS("a", []byte("a"), "custom string")

		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1:]

		TAssertEqual(n, 100)
		TAssertEqual(given, []string{
			"message: custom string",
			"given != expected",
			"given:    \"a\"",
			"expected: []byte{0x61}",
			"",
		})
	})
}

func test_TAssertEqualI() {
	TestStart("TAssertEqualI()")

	Testing("noop for equal slices", func() {
		TAssertEqualI([]string{}, []string{})
		TAssertEqualI([]string{"", "a", "b"}, []string{"", "a", "b"})
	})

	Testing("fail when `given` has less elements", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TAssertEqualI([]string{"a"}, []string{"a", "b", "c"})

		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1:]

		TAssertEqual(n, 100)
		TAssertEqual(given, []string{
			"expected has 2 more elements:",
			`[]string{"b", "c"}`,
			"",
		})
	})

	Testing("fail when `given` has more elements", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TAssertEqualI([]int{1, 2, 3, 4}, []int{5, 6, 7})

		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1:]

		TAssertEqual(n, 100)
		TAssertEqual(given, []string{
			"given has 1 more elements:",
			"[]int{4}",
			"",
		})
	})

	Testing("fail when nth element is different", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TAssertEqualI([]int{1, 2, 10, 4, 100}, []int{1, 2, 3, 4, 5})

		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")
		given = slices.Concat(given[1:4], given[5:])

		TAssertEqual(n, 100)
		TAssertEqual(given, []string{
			"given != expected (i = 2)",
			"given:    10",
			"expected: 3",
			"given != expected (i = 4)",
			"given:    100",
			"expected: 5",
			"",
		})
	})
}

func test_TErrorIf() {
	TestStart("TErrorIf()")

	Testing("noop on nil value", func() {
		exitFn := func(val int) {
			panic(val)
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TErrorIf(nil)
		testExitFn = savedExitFn
		testOutput = savedOutput

		TAssertEqual(w.String(), "")
	})

	Testing("simple dynamic message plus exit code", func() {
		myErr := errors.New("unexpected error")
		myStr := fmt.Sprintf("%#v", myErr)

		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TErrorIf(myErr)
		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1]

		TAssertEqual(n, 100)
		TAssertEqual(given, "Unexpected error: " + myStr)
	})
}

func test_TErrorNil() {
	TestStart("TErrorNil()")

	Testing("noop on thruthy value", func() {
		exitFn := func(val int) {
			panic(val)
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TErrorNil(errors.New("some error"))
		testExitFn = savedExitFn
		testOutput = savedOutput

		TAssertEqual(w.String(), "")
	})


	Testing("simple message with special exit code", func() {
		var n int
		exitFn := func(val int) {
			n = val
		}

		w := new(strings.Builder)

		savedExitFn := testExitFn
		savedOutput := testOutput
		testExitFn = exitFn
		testOutput = w

		TErrorNil(nil)
		testExitFn = savedExitFn
		testOutput = savedOutput

		given := strings.Split(w.String(), "\n")[1]

		TAssertEqual(n, 100)
		TAssertEqual(given, "Expected error, got nil")
	})
}

func test_SetLoggerOutput() {
	TestStart("SetLoggerOutput()")

	savedLogger := slog.Default()

	Testing("the output JSON has data under \"src\"", func() {
		saved := SourceInfoSkip
		SourceInfoSkip = 3

		s := new(strings.Builder)
		SetLoggerOutput(s)
		Info("", "")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		src  := data["src"].(map[string]interface{})
		file := src["file"].(string)
		const FILENAME = "tests/gobang.go"
		TAssertEqual(file[len(file) - len(FILENAME):], FILENAME)
		TAssertEqual(
			src["function"].(string),
			"gobang.test_SetLoggerOutput.func1",
		)
		line := src["line"].(float64)
		TAssertEqual(line > 0, true)

		SourceInfoSkip = saved
	})

	Testing("the output JSON has data under \"info\"", func() {
		s := new(strings.Builder)
		SetLoggerOutput(s)
		Info("", "")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		info := data["info"].(map[string]interface{})

		TAssertEqual(int(info["pid" ].(float64)), os.Getpid())
		TAssertEqual(int(info["ppid"].(float64)), os.Getppid())

		_, err = guuid.FromString(info["puuid"].(string))
		TErrorIf(err)
	})

	Testing("we can add groups to the default logger", func() {
		s := new(strings.Builder)
		SetLoggerOutput(s, slog.Group("one", "key", "value"))
		Info("", "")

		var data map[string]interface{}
		err := json.Unmarshal([]byte(s.String()), &data)
		TErrorIf(err)

		TAssertEqual(
			data["one"].(map[string]interface{})["key"].(string),
			"value",
		)
	})

	Testing("the puuid is the same across calls to the logger", func() {
		s := new(strings.Builder)
		SetLoggerOutput(s)
		Info("", "first")
		Info("", "second")

		strs := strings.Split(s.String(), "\n")
		TAssertEqual(len(strs), 3)
		TAssertEqual(strs[2], "")

		log1 := strs[0]
		log2 := strs[1]

		var puuidFromString = func(str string) string {
			var data map[string]interface{}
			err := json.Unmarshal([]byte(str), &data)
			TErrorIf(err)

			return data["info"].
				(map[string]interface{})["puuid"].(string)
		}

		puuid1 := puuidFromString(log1)
		puuid2 := puuidFromString(log2)
		TAssertEqual(puuid1, puuid2)

		uuid1, err := guuid.FromString(puuid1)
		TErrorIf(err)
		uuid2, err := guuid.FromString(puuid2)
		TErrorIf(err)
		TAssertEqual(uuid1, uuid2)
	})

	slog.SetDefault(savedLogger)
}

func test_levelFromString() {
	TestStart("levelFromString()")

	values := []string { "NONE", "ERROR", "WARNING", "INFO", "DEBUG" }
	Testing("ok for expected values", func() {
		for _, s := range values {
			var fallback LogLevel = 123
			theLevel := levelFromString(s, fallback)
			notFallback :=
				theLevel >= LevelNone &&
				theLevel <= LevelDebug &&
				theLevel != fallback
			TAssertEqual(notFallback, true)
		}
	})

	Testing("fallback for unexpected values", func() {
		var fallback LogLevel = 123
		rand, err := Random(10)
		TErrorIf(err)
		theLevel := levelFromString(string(rand), fallback)
		TAssertEqual(theLevel, fallback)
	})
}

func test_setLogLevel() {
	TestStart("setLogLevel()")

	const NAME = "LOG_LEVEL"
	savedEnvvar := os.Getenv(NAME)
	savedValue  := level
	var fallbackValue LogLevel = 123

	Testing("noop when envvar is unset", func() {
		TErrorIf(os.Unsetenv(NAME))
		level = fallbackValue

		setLogLevel()

		TAssertEqual(level, fallbackValue)
	})

	Testing("noop when envvar is empty", func() {
		TErrorIf(os.Setenv(NAME, ""))
		level = fallbackValue

		setLogLevel()

		TAssertEqual(level, fallbackValue)
	})

	Testing("update variable otherwise", func() {
		TErrorIf(os.Setenv(NAME, "DEBUG"))
		level = fallbackValue

		setLogLevel()

		TAssertEqual(level, LevelDebug)
	})

	TErrorIf(os.Setenv(NAME, savedEnvvar))
	level = savedValue
}

func test_SetLevel() {
	TestStart("SetLevel()")

	savedValue := level

	Testing("the behaviour is a simple assignment", func() {
		levels := []LogLevel {
			LevelNone,
			LevelError,
			LevelWarning,
			LevelInfo,
			LevelDebug,
		}
		for _, l := range levels {
			SetLevel(l)
			TAssertEqual(l, level)
		}
	})

	level = savedValue
}

func test_setMetric() {
	TestStart("setMetric()")

	const NAME = "NO_METRIC"
	savedEnvvar := os.Getenv(NAME)
	savedValue  := emitMetric
	defer func() {
		TErrorIf(os.Setenv(NAME, savedEnvvar))
		emitMetric = savedValue
	}()

	Testing("noop when envvar is unset", func() {
		TErrorIf(os.Unsetenv(NAME))
		emitMetric = true

		setMetric()

		TAssertEqual(emitMetric, true)
	})

	Testing("noop when envvar is empty", func() {
		TErrorIf(os.Setenv(NAME, ""))
		emitMetric = true

		setMetric()

		TAssertEqual(emitMetric, true)
	})

	Testing("make variable false otherwise", func() {
		TErrorIf(os.Setenv(NAME, "1"))
		emitMetric = true

		setMetric()

		TAssertEqual(emitMetric, false)
	})
}

func test_Fatal() {
	TestStart("Fatal()")

	Testing("error and panic", func() {
		savedLogger := slog.Default()
		savedLevel  := level

		w := new(strings.Builder)
		SetLoggerOutput(w)
		level = LevelError

		defer func() {
			r := recover()
			TAssertEqual(r == nil, false)

			slog.SetDefault(savedLogger)
			level = savedLevel

			TAssertEqual(len(w.String()) == 0, false)
		}()

		Fatal(nil)
		TErrorNil(nil)
	})
}

func test_FatalIf() {
	TestStart("FatalIf()")

	Testing("noop on nil", func() {
		FatalIf(nil)
	})

	Testing("error and panic otherwise", func() {
		savedLogger := slog.Default()
		savedLevel  := level

		w := new(strings.Builder)
		SetLoggerOutput(w)
		level = LevelError

		myErr := errors.New("the error")

		defer func() {
			r := recover()
			TAssertEqual(r, myErr)

			slog.SetDefault(savedLogger)
			level = savedLevel

			TAssertEqual(len(w.String()) == 0, false)
		}()

		FatalIf(myErr)
		TErrorNil(nil)
	})
}

func test_Assert() {
	TestStart("Assert()")

	Testing("noop if true", func() {
		Assert(true, "ignored")
	})

	Testing("error and panic if false", func() {
		savedLogger := slog.Default()
		savedLevel  := level

		w := new(strings.Builder)
		SetLoggerOutput(w)
		level = LevelError

		const errMsg = "assert error message"

		defer func() {
			r := recover()
			TAssertEqual(
				r.(error).Error(),
				"assertion failed: assert error message",
			)

			slog.SetDefault(savedLogger)
			level = savedLevel

			TAssertEqual(len(w.String()) == 0, false)
		}()

		Assert(1 == 2, errMsg)
		TErrorNil(nil)
	})
}

func test_Unreachable() {
	TestStart("Unreachable()")

	Testing("always has error and panic", func() {
		savedLogger := slog.Default()
		savedLevel  := level

		w := new(strings.Builder)
		SetLoggerOutput(w)
		level = LevelError

		defer func() {
			r := recover()
			TAssertEqual(
				r.(error).Error(),
				"assertion failed: Unreachable code was reached",
			)

			slog.SetDefault(savedLogger)
			level = savedLevel

			TAssertEqual(len(w.String()) == 0, false)
		}()

		Unreachable()
		TErrorNil(nil)
	})
}

func test_setHostname() {
	TestStart("setHostname()")

	Testing("it assigns the value to the global variable", func() {
		name, _ := os.Hostname()
		hostname = ""
		setHostname()
		TAssertEqual(hostname, name)
	})
}



func MainTest() {
	Init()

	test_SetOf()
	test_Contains()
	test_MapIndexed()
	test_Map()
	test_Filter()
	test_PanicIf()
	test_Must()
	test_Clamp()
	test_ValidateSQLTablePrefix()
	test_WrapErrors()
	test_SomeError()
	test_SomeFnError()
	test_Random()
	test_sourceInfo()
	test_logArgs()
	test_anyArr()
	test_Debug()
	test_Info()
	test_Warning()
	test_Error()
	test_metric()
	test_Timed()
	test_MakeCounter()
	test_MakeGauge()
	test_showColour()
	test_TestStart()
	test_Testing()
	test_terr()
	test_TAssertEqual()
	test_TAssertEqualS()
	test_TAssertEqualI()
	test_TErrorIf()
	test_TErrorNil()
	test_SetLoggerOutput()
	test_levelFromString()
	test_setLogLevel()
	test_SetLevel()
	test_setMetric()
	test_Fatal()
	test_FatalIf()
	test_Assert()
	test_Unreachable()
	test_setHostname()
}