package db

import (
	"math"
	"testing"
)

// ─────────────────────────────────────────────
// classifyDBType
// ─────────────────────────────────────────────
func TestClassifyDBType(t *testing.T) {
	cases := []struct {
		typeName string
		want     int
	}{
		// MySQL 整数类型
		{"INT", dbTypeInteger},
		{"TINYINT", dbTypeInteger},
		{"SMALLINT", dbTypeInteger},
		{"MEDIUMINT", dbTypeInteger},
		{"BIGINT", dbTypeInteger},
		{"INT UNSIGNED", dbTypeInteger},
		{"BIGINT UNSIGNED", dbTypeInteger},
		{"TINYINT(1)", dbTypeInteger},
		{"YEAR", dbTypeInteger},
		{"BOOL", dbTypeInteger},
		{"BOOLEAN", dbTypeInteger},

		// PostgreSQL 整数类型
		{"INT2", dbTypeInteger},
		{"INT4", dbTypeInteger},
		{"INT8", dbTypeInteger},
		{"SERIAL", dbTypeInteger},
		{"BIGSERIAL", dbTypeInteger},
		{"SMALLSERIAL", dbTypeInteger},
		{"OID", dbTypeInteger},

		// DECIMAL / NUMERIC
		{"DECIMAL", dbTypeDecimal},
		{"DECIMAL(10,2)", dbTypeDecimal},
		{"NUMERIC", dbTypeDecimal},
		{"NUMERIC(8,4)", dbTypeDecimal},
		{"NEWDECIMAL", dbTypeDecimal},

		// FLOAT / DOUBLE
		{"FLOAT", dbTypeFloat},
		{"DOUBLE", dbTypeFloat},
		{"REAL", dbTypeFloat},
		{"FLOAT4", dbTypeFloat},
		{"FLOAT8", dbTypeFloat},
		{"DOUBLE PRECISION", dbTypeFloat},

		// 未知类型
		{"VARCHAR", dbTypeUnknown},
		{"TEXT", dbTypeUnknown},
		{"DATETIME", dbTypeUnknown},
		{"TIMESTAMP", dbTypeUnknown},
		{"BLOB", dbTypeUnknown},
		{"", dbTypeUnknown},
	}

	for _, c := range cases {
		t.Run(c.typeName, func(t *testing.T) {
			got := classifyDBType(c.typeName)
			if got != c.want {
				t.Errorf("classifyDBType(%q) = %d, want %d", c.typeName, got, c.want)
			}
		})
	}
}

// ─────────────────────────────────────────────
// fixFloatValue
// ─────────────────────────────────────────────
func TestFixFloatValue(t *testing.T) {
	t.Run("integer category: round to int64", func(t *testing.T) {
		// 这是核心场景：float64 精度噪声导致整数变为 1.9999...
		got := fixFloatValue(1.9999999999999998, dbTypeInteger, 0)
		if got != int64(2) {
			t.Errorf("got %v (%T), want int64(2)", got, got)
		}
	})

	t.Run("integer category: 2.0000000000001 rounds to 2", func(t *testing.T) {
		got := fixFloatValue(2.0000000000001, dbTypeInteger, 0)
		if got != int64(2) {
			t.Errorf("got %v (%T), want int64(2)", got, got)
		}
	})

	t.Run("decimal category: scale=2 roundtrip precision", func(t *testing.T) {
		got := fixFloatValue(1.1999999999999999, dbTypeDecimal, 2)
		f, ok := got.(float64)
		if !ok {
			t.Fatalf("expected float64, got %T", got)
		}
		if f != 1.2 {
			t.Errorf("got %v, want 1.2", f)
		}
	})

	t.Run("decimal category: scale=2, 1.20000000001 -> 1.2", func(t *testing.T) {
		got := fixFloatValue(1.20000000001, dbTypeDecimal, 2)
		f := got.(float64)
		if f != 1.2 {
			t.Errorf("got %v, want 1.2", f)
		}
	})

	t.Run("decimal category: scale=-1 (unknown), no modification", func(t *testing.T) {
		got := fixFloatValue(1.23456789, dbTypeDecimal, -1)
		if got != 1.23456789 {
			t.Errorf("got %v, want 1.23456789", got)
		}
	})

	t.Run("decimal category: scale=0, round to whole number", func(t *testing.T) {
		got := fixFloatValue(2.7, dbTypeDecimal, 0)
		if got != float64(3) {
			t.Errorf("got %v (%T), want float64(3)", got, got)
		}
	})

	t.Run("float category: scale=-1 no modification", func(t *testing.T) {
		got := fixFloatValue(3.14159265, dbTypeFloat, -1)
		if got != 3.14159265 {
			t.Errorf("got %v, want 3.14159265", got)
		}
	})

	t.Run("unknown category: passthrough", func(t *testing.T) {
		got := fixFloatValue(99.9, dbTypeUnknown, -1)
		if got != 99.9 {
			t.Errorf("got %v, want 99.9", got)
		}
	})

	t.Run("NaN -> 0", func(t *testing.T) {
		got := fixFloatValue(math.NaN(), dbTypeInteger, 0)
		if got != float64(0) {
			t.Errorf("got %v, want 0", got)
		}
	})

	t.Run("+Inf -> 0", func(t *testing.T) {
		got := fixFloatValue(math.Inf(1), dbTypeDecimal, 2)
		if got != float64(0) {
			t.Errorf("got %v, want 0", got)
		}
	})
}

// ─────────────────────────────────────────────
// roundFloat
// ─────────────────────────────────────────────
func TestRoundFloat(t *testing.T) {
	t.Run("scale=2: 1.19999... -> 1.2", func(t *testing.T) {
		got := roundFloat(1.1999999999999999, 2)
		if got != float64(1.2) {
			t.Errorf("got %v, want 1.2", got)
		}
	})

	t.Run("scale=2: 1.20000...1 -> 1.2", func(t *testing.T) {
		got := roundFloat(1.20000000001, 2)
		if got != float64(1.2) {
			t.Errorf("got %v, want 1.2", got)
		}
	})

	t.Run("scale=0: round to integer float", func(t *testing.T) {
		got := roundFloat(2.5, 0)
		if got != float64(3) {
			t.Errorf("got %v, want 3.0", got)
		}
	})

	t.Run("scale=-1: passthrough unchanged", func(t *testing.T) {
		got := roundFloat(1.23456789, -1)
		if got != 1.23456789 {
			t.Errorf("got %v, want 1.23456789", got)
		}
	})

	t.Run("NaN -> 0", func(t *testing.T) {
		got := roundFloat(math.NaN(), 2)
		if got != float64(0) {
			t.Errorf("got %v, want 0", got)
		}
	})
}

// ─────────────────────────────────────────────
// convertBytes
// ─────────────────────────────────────────────
func TestConvertBytes(t *testing.T) {
	t.Run("integer category: '2' -> int64(2)", func(t *testing.T) {
		got := convertBytes([]byte("2"), dbTypeInteger, 0)
		if got != int64(2) {
			t.Errorf("got %v (%T), want int64(2)", got, got)
		}
	})

	t.Run("integer category: '2.00' -> int64(2)", func(t *testing.T) {
		got := convertBytes([]byte("2.00"), dbTypeInteger, 0)
		if got != int64(2) {
			t.Errorf("got %v (%T), want int64(2)", got, got)
		}
	})

	t.Run("decimal category: '1.20' scale=2 -> float64(1.2)", func(t *testing.T) {
		got := convertBytes([]byte("1.20"), dbTypeDecimal, 2)
		if got != float64(1.2) {
			t.Errorf("got %v (%T), want float64(1.2)", got, got)
		}
	})

	t.Run("decimal category: '0.00' scale=2 -> float64(0)", func(t *testing.T) {
		got := convertBytes([]byte("0.00"), dbTypeDecimal, 2)
		if got != float64(0) {
			t.Errorf("got %v (%T), want float64(0)", got, got)
		}
	})

	t.Run("float category: '3.14' scale=-1 -> float64(3.14)", func(t *testing.T) {
		got := convertBytes([]byte("3.14"), dbTypeFloat, -1)
		if got != float64(3.14) {
			t.Errorf("got %v (%T), want float64(3.14)", got, got)
		}
	})

	t.Run("unknown category: passthrough as string", func(t *testing.T) {
		got := convertBytes([]byte("hello"), dbTypeUnknown, 0)
		if got != "hello" {
			t.Errorf("got %v (%T), want 'hello'", got, got)
		}
	})

	t.Run("integer category: invalid bytes -> string fallback", func(t *testing.T) {
		got := convertBytes([]byte("abc"), dbTypeInteger, 0)
		if got != "abc" {
			t.Errorf("got %v (%T), want 'abc'", got, got)
		}
	})
}