// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

package hlcpp

import (
	"fmt"
	"strings"

	gidlir "go.fuchsia.dev/fuchsia/tools/fidl/gidl/ir"
	gidlmixer "go.fuchsia.dev/fuchsia/tools/fidl/gidl/mixer"
	"go.fuchsia.dev/fuchsia/tools/fidl/lib/fidlgen"
)

func BuildEqualityCheck(actualExpr string, expectedValue gidlir.Value, decl gidlmixer.Declaration, handleKoidVectorName string) string {
	builder := equalityCheckBuilder{
		handleKoidVectorName: handleKoidVectorName,
	}
	builder.visit(actualExpr, expectedValue, decl)
	return builder.String()
}

// Generator of new variable names from a sequence.
type varSeq int

func (v *varSeq) next() string {
	*v++
	return fmt.Sprintf("f%d", *v)
}

type equalityCheckBuilder struct {
	strings.Builder
	varSeq varSeq
	// Name of a C++ variable containing an vector of zx_koid_t of handle values
	// This is read-only and is used for checking handle koid equality.
	handleKoidVectorName string
}

func (b *equalityCheckBuilder) write(format string, vals ...interface{}) {
	b.WriteString(fmt.Sprintf(format, vals...))
}

func (b *equalityCheckBuilder) createAndAssignVar(val string) string {
	varName := b.varSeq.next()
	b.write("[[maybe_unused]] auto& %s = %s;\n", varName, val)
	return varName
}

func (b *equalityCheckBuilder) construct(typename string, fmtStr string, args ...interface{}) string {
	return fmt.Sprintf("%s(%s)", typename, fmt.Sprintf(fmtStr, args...))
}

func (b *equalityCheckBuilder) assertEquals(actual, expected string) {
	b.write("ASSERT_EQ(%s, %s);\n", actual, expected)
}
func (b *equalityCheckBuilder) assertStringEquals(actual, expected string) {
	b.write("ASSERT_STR_EQ(%s, %s);\n", actual, expected)
}
func (b *equalityCheckBuilder) assertNotEquals(actual, expected string) {
	b.write("ASSERT_NE(%s, %s);\n", actual, expected)
}
func (b *equalityCheckBuilder) assertFalse(value string) {
	b.write("ASSERT_FALSE(%s);\n", value)
}
func (b *equalityCheckBuilder) assertTrue(value string) {
	b.write("ASSERT_TRUE(%s);\n", value)
}
func (b *equalityCheckBuilder) assertNull(value string) {
	b.write("ASSERT_NULL(%s);\n", value)
}

func (b *equalityCheckBuilder) visit(actualExpr string, expectedValue gidlir.Value, decl gidlmixer.Declaration) {
	switch expectedValue := expectedValue.(type) {
	case bool:
		b.assertEquals(actualExpr, b.construct(typeName(decl), "%t", expectedValue))
		return
	case int64, uint64, float64:
		switch decl := decl.(type) {
		case gidlmixer.PrimitiveDeclaration, *gidlmixer.EnumDecl:
			b.assertEquals(actualExpr, b.construct(typeName(decl), formatPrimitive(expectedValue)))
			return
		case *gidlmixer.BitsDecl:
			b.assertEquals(actualExpr, fmt.Sprintf("static_cast<%s>(%s)", declName(decl), formatPrimitive(expectedValue)))
			return
		}
	case gidlir.RawFloat:
		switch decl.(*gidlmixer.FloatDecl).Subtype() {
		case fidlgen.Float32:
			b.assertEquals(actualExpr, fmt.Sprintf("([] { uint32_t u = %#b; float f; memcpy(&f, &u, sizeof(float)); return f; })()", expectedValue))
			return
		case fidlgen.Float64:
			b.assertEquals(actualExpr, fmt.Sprintf("([] { uint64_t u = %#b; double d; memcpy(&d, &u, sizeof(double)); return d; })()", expectedValue))
			return
		}
	case string:
		dereferencedActual := actualExpr
		if decl.IsNullable() {
			dereferencedActual = fmt.Sprintf("(*%s)", actualExpr)
		}
		b.assertStringEquals(dereferencedActual, escapeStr(expectedValue))
		return
	case gidlir.HandleWithRights:
		b.visitHandle(actualExpr, expectedValue, decl.(*gidlmixer.HandleDecl))
		return
	case gidlir.Record:
		switch decl := decl.(type) {
		case *gidlmixer.StructDecl:
			b.visitStruct(actualExpr, expectedValue, decl)
			return
		case *gidlmixer.TableDecl:
			b.visitTable(actualExpr, expectedValue, decl)
			return
		case *gidlmixer.UnionDecl:
			b.visitUnion(actualExpr, expectedValue, decl)
			return
		}
	case []gidlir.Value:
		b.visitList(actualExpr, expectedValue, decl.(gidlmixer.ListDeclaration))
		return
	case nil:
		switch decl.(type) {
		case *gidlmixer.StringDecl:
			b.assertNull(actualExpr)
			return
		case *gidlmixer.HandleDecl:
			b.assertFalse(fmt.Sprintf("%s.is_valid()", actualExpr))
			return
		case *gidlmixer.UnionDecl:
			b.assertNull(actualExpr)
			return
		case *gidlmixer.VectorDecl:
			b.assertFalse(fmt.Sprintf("%s.has_value()", actualExpr))
			return
		case *gidlmixer.StructDecl:
			b.assertNull(actualExpr)
			return
		}
	}
	panic(fmt.Sprintf("not implemented: %T (decl: %T)", expectedValue, decl))
}

func (b *equalityCheckBuilder) visitHandle(actualExpr string, expectedValue gidlir.HandleWithRights, decl *gidlmixer.HandleDecl) {
	actualVar := b.createAndAssignVar(actualExpr)
	resultVar := b.varSeq.next()
	// Check:
	// - Original handle's koid matches final handle (it could be replaced so can't check handle value).
	// - Type matches expectation.
	// - Rights matches expectation.
	b.write(`
	zx_info_handle_basic_t %[1]s_info;
	ASSERT_OK(zx_object_get_info(%[2]s.get(), ZX_INFO_HANDLE_BASIC, &%[1]s_info, sizeof(%[1]s_info), nullptr, nullptr));
	ASSERT_EQ(%[1]s_info.koid, %[3]s[%[4]d]);
	ASSERT_TRUE(%[1]s_info.type == %[5]d || %[5]d == ZX_OBJ_TYPE_NONE);
	ASSERT_TRUE(%[1]s_info.rights == %[6]d || %[6]d == ZX_RIGHT_SAME_RIGHTS);
  `, resultVar, actualVar, b.handleKoidVectorName, expectedValue.Handle, expectedValue.Type, expectedValue.Rights)
}

func (b *equalityCheckBuilder) visitStruct(actualExpr string, expectedValue gidlir.Record, decl *gidlmixer.StructDecl) {
	op := "."
	if decl.IsNullable() {
		op = "->"
	}
	actualVar := b.createAndAssignVar(actualExpr)
	for _, field := range expectedValue.Fields {
		fieldDecl, ok := decl.Field(field.Key.Name)
		if !ok {
			panic(fmt.Sprintf("field %q not found", field.Key.Name))
		}
		actualFieldExpr := fmt.Sprintf("%s%s%s", actualVar, op, field.Key.Name)
		b.visit(actualFieldExpr, field.Value, fieldDecl)
	}
}

func (b *equalityCheckBuilder) visitTable(actualExpr string, expectedValue gidlir.Record, decl *gidlmixer.TableDecl) {
	actualVar := b.createAndAssignVar(actualExpr)
	expectedFieldValues := map[string]gidlir.Value{}
	for _, field := range expectedValue.Fields {
		if field.Key.IsUnknown() {
			unknownData := fmt.Sprintf("%s.UnknownData()", actualVar)
			b.assertNotEquals(
				fmt.Sprintf("%s.find(%d)", unknownData, field.Key.UnknownOrdinal),
				fmt.Sprintf("%s.end()", unknownData))
			if decl.IsResourceType() {
				b.visitUnknownBytes(
					fmt.Sprintf("%s.at(%d).bytes", unknownData, field.Key.UnknownOrdinal),
					field.Value.(gidlir.UnknownData).Bytes)
				b.visitUnknownHandles(
					fmt.Sprintf("%s.at(%d).handles", unknownData, field.Key.UnknownOrdinal),
					field.Value.(gidlir.UnknownData).Handles)
			} else {
				b.visitUnknownBytes(
					fmt.Sprintf("%s.at(%d)", unknownData, field.Key.UnknownOrdinal),
					field.Value.(gidlir.UnknownData).Bytes)
			}
		} else {
			expectedFieldValues[field.Key.Name] = field.Value
		}
	}
	for _, fieldName := range decl.FieldNames() {
		fieldDecl, ok := decl.Field(fieldName)
		if !ok {
			panic(fmt.Sprintf("field decl %s not found", fieldName))
		}
		if expectedFieldValue, ok := expectedFieldValues[fieldName]; ok {
			b.assertTrue(fmt.Sprintf("%s.has_%s()", actualVar, fieldName))
			actualFieldExpr := fmt.Sprintf("%s.%s()", actualVar, fieldName)
			b.visit(actualFieldExpr, expectedFieldValue, fieldDecl)
		} else {
			b.assertFalse(fmt.Sprintf("%s.has_%s()", actualVar, fieldName))
		}
	}
}

func (b *equalityCheckBuilder) visitUnion(actualExpr string, expectedValue gidlir.Record, decl *gidlmixer.UnionDecl) {
	op := "."
	if decl.IsNullable() {
		op = "->"
	}
	actualVar := b.createAndAssignVar(actualExpr)
	if len(expectedValue.Fields) != 1 {
		panic("shouldn't happen")
	}
	field := expectedValue.Fields[0]
	if field.Key.IsUnknown() {
		b.visitUnknownBytes(
			fmt.Sprintf("(*%s.UnknownBytes())", actualExpr),
			field.Value.(gidlir.UnknownData).Bytes)
		if decl.IsResourceType() {
			b.visitUnknownHandles(
				fmt.Sprintf("(*%s.UnknownHandles())", actualExpr),
				field.Value.(gidlir.UnknownData).Handles)
		}
		return
	}
	fieldDecl, ok := decl.Field(field.Key.Name)
	if !ok {
		panic(fmt.Sprintf("field %q not found", field.Key.Name))
	}
	b.assertEquals(
		fmt.Sprintf("%s%sWhich()", actualVar, op),
		fmt.Sprintf("%s::Tag::k%s", declName(decl), fidlgen.ToUpperCamelCase(field.Key.Name)))
	actualFieldExpr := fmt.Sprintf("%s%s%s()", actualVar, op, field.Key.Name)
	b.visit(actualFieldExpr, field.Value, fieldDecl)
}

func (b *equalityCheckBuilder) visitList(actualExpr string, expectedValue []gidlir.Value, decl gidlmixer.ListDeclaration) {
	var actualVar string
	if decl.IsNullable() {
		actualVar = b.createAndAssignVar(actualExpr + ".value()")
	} else {
		actualVar = b.createAndAssignVar(actualExpr)
	}
	if _, ok := decl.(*gidlmixer.VectorDecl); ok {
		b.assertEquals(fmt.Sprintf("%s.size()", actualVar), fmt.Sprintf("%d", len(expectedValue)))
	}
	for i, item := range expectedValue {
		lhs := fmt.Sprintf("%s[%d]", actualVar, i)
		switch item.(type) {
		case bool:
			// prevents `error: no viable conversion from '__bit_iterator<std::vector<bool>, false>' to 'const void *'`
			lhs = fmt.Sprintf("bool(%s)", lhs)
		}
		b.visit(lhs, item, decl.Elem())
	}
}

func (b *equalityCheckBuilder) visitUnknownBytes(actualExpr string, expectedValue []byte) {
	b.write(`
	std::vector<uint8_t> bytes%[1]s = %[2]s;
	ASSERT_EQ(bytes%[1]s, %[3]s);
	`,
		b.varSeq.next(), BuildBytes(expectedValue), actualExpr)
}

func (b *equalityCheckBuilder) visitUnknownHandles(actualExpr string, expectedValue []gidlir.Handle) {
	b.write(`
	std::vector<zx_handle_t> handles%[1]s = %[2]s;
	ASSERT_EQ(handles%[1]s.size(), %[3]s.size());
	for (uint32_t i = 0; i < handles%[1]s.size(); ++i) {
		zx_handle_t actual = handles%[1]s[i];
		zx_info_handle_basic_t %[1]s_info_actual;
		ASSERT_OK(zx_object_get_info(actual, ZX_INFO_HANDLE_BASIC, &%[1]s_info_actual, sizeof(%[1]s_info_actual), nullptr, nullptr));

		zx_handle_t expected = %[3]s[i].get();
		zx_info_handle_basic_t %[1]s_info_expected;
		ASSERT_OK(zx_object_get_info(expected, ZX_INFO_HANDLE_BASIC, &%[1]s_info_expected, sizeof(%[1]s_info_expected), nullptr, nullptr));

		ASSERT_EQ(%[1]s_info_expected.koid, %[1]s_info_actual.koid);
	}
	`, b.varSeq.next(), BuildRawHandlesFromHandleInfos(expectedValue), actualExpr)
}

func formatPrimitive(value gidlir.Value) string {
	switch value := value.(type) {
	case int64:
		if value == -9223372036854775808 {
			return "-9223372036854775807ll - 1"
		}
		return fmt.Sprintf("%dll", value)
	case uint64:
		return fmt.Sprintf("%dull", value)
	case float64:
		return fmt.Sprintf("%g", value)
	}
	panic("Unreachable")
}