/*
 * Copyright 2020 Google LLC
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/sksl/SkSLDehydrator.h"

#include "include/core/SkSpan.h"
#include "include/private/SkSLDefines.h"
#include "include/private/SkSLLayout.h"
#include "include/private/SkSLModifiers.h"
#include "include/private/SkSLProgramElement.h"
#include "include/private/SkSLStatement.h"
#include "include/private/SkSLSymbol.h"
#include "include/private/SkTArray.h"
#include "include/sksl/SkSLOperator.h"
#include "src/sksl/SkSLOutputStream.h"
#include "src/sksl/SkSLProgramSettings.h"
#include "src/sksl/SkSLRehydrator.h"
#include "src/sksl/ir/SkSLBinaryExpression.h"
#include "src/sksl/ir/SkSLBlock.h"
#include "src/sksl/ir/SkSLConstructorArray.h"
#include "src/sksl/ir/SkSLConstructorArrayCast.h"
#include "src/sksl/ir/SkSLConstructorCompound.h"
#include "src/sksl/ir/SkSLConstructorCompoundCast.h"
#include "src/sksl/ir/SkSLConstructorDiagonalMatrix.h"
#include "src/sksl/ir/SkSLConstructorMatrixResize.h"
#include "src/sksl/ir/SkSLConstructorScalarCast.h"
#include "src/sksl/ir/SkSLConstructorSplat.h"
#include "src/sksl/ir/SkSLConstructorStruct.h"
#include "src/sksl/ir/SkSLDoStatement.h"
#include "src/sksl/ir/SkSLExpression.h"
#include "src/sksl/ir/SkSLExpressionStatement.h"
#include "src/sksl/ir/SkSLField.h"
#include "src/sksl/ir/SkSLFieldAccess.h"
#include "src/sksl/ir/SkSLForStatement.h"
#include "src/sksl/ir/SkSLFunctionCall.h"
#include "src/sksl/ir/SkSLFunctionDeclaration.h"
#include "src/sksl/ir/SkSLFunctionDefinition.h"
#include "src/sksl/ir/SkSLFunctionPrototype.h"
#include "src/sksl/ir/SkSLIfStatement.h"
#include "src/sksl/ir/SkSLIndexExpression.h"
#include "src/sksl/ir/SkSLInterfaceBlock.h"
#include "src/sksl/ir/SkSLLiteral.h"
#include "src/sksl/ir/SkSLPostfixExpression.h"
#include "src/sksl/ir/SkSLPrefixExpression.h"
#include "src/sksl/ir/SkSLProgram.h"
#include "src/sksl/ir/SkSLReturnStatement.h"
#include "src/sksl/ir/SkSLSetting.h"
#include "src/sksl/ir/SkSLStructDefinition.h"
#include "src/sksl/ir/SkSLSwitchCase.h"
#include "src/sksl/ir/SkSLSwitchStatement.h"
#include "src/sksl/ir/SkSLSwizzle.h"
#include "src/sksl/ir/SkSLSymbolTable.h"
#include "src/sksl/ir/SkSLTernaryExpression.h"
#include "src/sksl/ir/SkSLType.h"
#include "src/sksl/ir/SkSLUnresolvedFunction.h"
#include "src/sksl/ir/SkSLVarDeclarations.h"
#include "src/sksl/ir/SkSLVariable.h"
#include "src/sksl/ir/SkSLVariableReference.h"

#include <map>

namespace SkSL {

static constexpr int HEADER_SIZE = 2;

class AutoDehydratorSymbolTable {
public:
    AutoDehydratorSymbolTable(Dehydrator* dehydrator, const std::shared_ptr<SymbolTable>& symbols)
        : fDehydrator(dehydrator) {
        dehydrator->fSymbolMap.emplace_back();
        if (symbols) {
            dehydrator->write(*symbols);
        } else {
            dehydrator->writeCommand(Rehydrator::kVoid_Command);
        }
    }

    ~AutoDehydratorSymbolTable() {
        fDehydrator->fSymbolMap.pop_back();
    }

private:
    Dehydrator* fDehydrator;
};

void Dehydrator::writeId(const Symbol* s) {
    uint16_t id = this->symbolId(s);
    if (id) {
        this->writeU16(id);
    } else {
        this->writeU16(Rehydrator::kBuiltin_Symbol);
        this->write(s->name());
    }
}

void Dehydrator::write(Layout l) {
    if (l == Layout()) {
        this->writeCommand(Rehydrator::kDefaultLayout_Command);
    } else if (l == Layout::builtin(l.fBuiltin)) {
        this->writeCommand(Rehydrator::kBuiltinLayout_Command);
        this->writeS16(l.fBuiltin);
    } else {
        this->writeCommand(Rehydrator::kLayout_Command);
        fBody.write32(l.fFlags);
        this->writeS8(l.fLocation);
        this->writeS16(l.fOffset);
        this->writeS16(l.fBinding);
        this->writeS8(l.fIndex);
        this->writeS8(l.fSet);
        this->writeS16(l.fBuiltin);
        this->writeS8(l.fInputAttachmentIndex);
    }
}

void Dehydrator::write(Modifiers m) {
    if (m == Modifiers()) {
        this->writeCommand(Rehydrator::kDefaultModifiers_Command);
    } else {
        if (m.fFlags <= 255) {
            this->writeCommand(Rehydrator::kModifiers8Bit_Command);
            this->write(m.fLayout);
            this->writeU8(m.fFlags);
        } else {
            this->writeCommand(Rehydrator::kModifiers_Command);
            this->write(m.fLayout);
            this->writeS32(m.fFlags);
        }
    }
}

void Dehydrator::write(std::string_view s) {
    this->write(std::string(s));
}

void Dehydrator::write(std::string s) {
    auto found = fStrings.find(s);
    int offset;
    if (found == fStrings.end()) {
        offset = fStringBuffer.bytesWritten() + HEADER_SIZE;
        fStrings.insert({ s, offset });
        SkASSERT(s.length() <= 255);
        fStringBreaks.add(fStringBuffer.bytesWritten());
        fStringBuffer.write8(s.length());
        fStringBuffer.writeString(s);
    } else {
        offset = found->second;
    }
    this->writeU16(offset);
}

void Dehydrator::write(const Symbol& s) {
    uint16_t id = this->symbolId(&s);
    if (id) {
        this->writeCommand(Rehydrator::kSymbolRef_Command);
        this->writeU16(id);
        return;
    }
    switch (s.kind()) {
        case Symbol::Kind::kFunctionDeclaration: {
            this->allocSymbolId(&s);
            const FunctionDeclaration& f = s.as<FunctionDeclaration>();
            this->writeCommand(Rehydrator::kFunctionDeclaration_Command);
            this->writeId(&f);
            this->write(f.modifiers());
            this->write(f.name());
            this->writeU8(f.parameters().size());
            for (const Variable* p : f.parameters()) {
                this->write(*p);
            }
            this->write(f.returnType());
            break;
        }
        case Symbol::Kind::kUnresolvedFunction: {
            this->allocSymbolId(&s);
            const UnresolvedFunction& f = s.as<UnresolvedFunction>();
            this->writeCommand(Rehydrator::kUnresolvedFunction_Command);
            this->writeId(&f);
            this->writeU8(f.functions().size());
            for (const FunctionDeclaration* funcDecl : f.functions()) {
                this->write(*funcDecl);
            }
            break;
        }
        case Symbol::Kind::kType: {
            const Type& t = s.as<Type>();
            switch (t.typeKind()) {
                case Type::TypeKind::kArray:
                    this->allocSymbolId(&s);
                    this->writeCommand(Rehydrator::kArrayType_Command);
                    this->writeId(&t);
                    this->write(t.componentType());
                    this->writeS8(t.columns());
                    break;
                case Type::TypeKind::kStruct:
                    this->allocSymbolId(&s);
                    this->writeCommand(Rehydrator::kStructType_Command);
                    this->writeId(&t);
                    this->write(t.name());
                    this->writeU8(t.fields().size());
                    for (const Type::Field& f : t.fields()) {
                        this->write(f.fModifiers);
                        this->write(f.fName);
                        this->write(*f.fType);
                    }
                    this->writeU8(t.isInterfaceBlock());
                    break;
                default:
                    this->writeCommand(Rehydrator::kSymbolRef_Command);
                    this->writeU16(Rehydrator::kBuiltin_Symbol);
                    this->write(t.name());
                    break;
            }
            break;
        }
        case Symbol::Kind::kVariable: {
            this->allocSymbolId(&s);
            const Variable& v = s.as<Variable>();
            this->writeCommand(Rehydrator::kVariable_Command);
            this->writeId(&v);
            this->write(v.modifiers());
            this->write(v.name());
            this->write(v.type());
            this->writeU8((int8_t) v.storage());
            break;
        }
        case Symbol::Kind::kField: {
            const Field& f = s.as<Field>();
            this->writeCommand(Rehydrator::kField_Command);
            this->writeU16(this->symbolId(&f.owner()));
            this->writeU8(f.fieldIndex());
            break;
        }
        case Symbol::Kind::kExternal:
            SkASSERT(false);
            break;
    }
}

void Dehydrator::write(const SymbolTable& symbols) {
    auto symbolIsReferenced = [&](const Symbol& sym) -> bool {
        if (sym.is<Variable>()) {
            // Only dehydrate Variables that haven't been optimized away.
            return sym.as<Variable>().storage() != VariableStorage::kEliminated;
        }

        // Only dehydrate symbols that are actually findable by name. Some symbols can be left
        // behind and inaccessible, such as stale UnresolvedFunction nodes; we don't need to
        // store and rehydrate those.
        const Symbol** found = symbols.fSymbols.find(SymbolTable::MakeSymbolKey(sym.name()));
        return found && *found == &sym;
    };

    this->writeCommand(Rehydrator::kSymbolTable_Command);
    this->writeU8(symbols.isBuiltin());

    // Make a list of all the owned symbols which are referenced.
    std::vector<const Symbol*> ownedSymbols;
    std::vector<const Symbol*> discardedSymbols;
    for (const std::unique_ptr<const Symbol>& s : symbols.fOwnedSymbols) {
        if (symbolIsReferenced(*s)) {
            ownedSymbols.push_back(s.get());
        }
    }

    // Write the owned symbols.
    this->writeU16(ownedSymbols.size());
    for (const Symbol* s : ownedSymbols) {
        this->write(*s);
    }

    // Make an ordered list of every referenced symbol in the symbol-table, owned or not.
    std::map<std::string_view, const Symbol*> ordered;
    symbols.foreach([&](std::string_view name, const Symbol* symbol) {
        if (symbolIsReferenced(*symbol)) {
            ordered.insert({name, symbol});
        }
    });

    // List the symbols in named order.
    this->writeU16(ordered.size());
    for (const auto& [name, symbol] : ordered) {
        bool found = false;
        for (size_t i = 0; i < ownedSymbols.size(); ++i) {
            if (ownedSymbols[i] == symbol) {
                fCommandBreaks.add(fBody.bytesWritten());
                this->writeU16(i);
                found = true;
                break;
            }
        }
        if (!found) {
            // we should only fail to find builtin types
            SkASSERT(symbol->is<Type>() && symbol->as<Type>().isInBuiltinTypes());
            this->writeU16(Rehydrator::kBuiltin_Symbol);
            this->write(symbol->name());
        }
    }
}

void Dehydrator::writeExpressionSpan(const SkSpan<const std::unique_ptr<Expression>>& span) {
    this->writeU8(span.size());
    for (const auto& expr : span) {
        this->write(expr.get());
    }
}

void Dehydrator::write(const Expression* e) {
    if (e) {
        switch (e->kind()) {
            case Expression::Kind::kBinary: {
                const BinaryExpression& b = e->as<BinaryExpression>();
                this->writeCommand(Rehydrator::kBinary_Command);
                this->write(b.left().get());
                this->writeU8((int) b.getOperator().kind());
                this->write(b.right().get());
                break;
            }
            case Expression::Kind::kChildCall:
                SkDEBUGFAIL("unimplemented--not expected to be used from within an include file");
                break;

            case Expression::Kind::kConstructorArray:
                this->writeCommand(Rehydrator::kConstructorArray_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorArray>().argumentSpan());
                break;

            case Expression::Kind::kConstructorArrayCast:
                this->writeCommand(Rehydrator::kConstructorArrayCast_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorArrayCast>().argumentSpan());
                break;

            case Expression::Kind::kConstructorCompound:
                this->writeCommand(Rehydrator::kConstructorCompound_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorCompound>().argumentSpan());
                break;

            case Expression::Kind::kConstructorCompoundCast:
                this->writeCommand(Rehydrator::kConstructorCompoundCast_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorCompoundCast>().argumentSpan());
                break;

            case Expression::Kind::kConstructorDiagonalMatrix:
                this->writeCommand(Rehydrator::kConstructorDiagonalMatrix_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorDiagonalMatrix>().argumentSpan());
                break;

            case Expression::Kind::kConstructorMatrixResize:
                this->writeCommand(Rehydrator::kConstructorMatrixResize_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorMatrixResize>().argumentSpan());
                break;

            case Expression::Kind::kConstructorScalarCast:
                this->writeCommand(Rehydrator::kConstructorScalarCast_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorScalarCast>().argumentSpan());
                break;

            case Expression::Kind::kConstructorSplat:
                this->writeCommand(Rehydrator::kConstructorSplat_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorSplat>().argumentSpan());
                break;

            case Expression::Kind::kConstructorStruct:
                this->writeCommand(Rehydrator::kConstructorStruct_Command);
                this->write(e->type());
                this->writeExpressionSpan(e->as<ConstructorStruct>().argumentSpan());
                break;

            case Expression::Kind::kExternalFunctionCall:
            case Expression::Kind::kExternalFunctionReference:
                SkDEBUGFAIL("unimplemented--not expected to be used from within an include file");
                break;

            case Expression::Kind::kFieldAccess: {
                const FieldAccess& f = e->as<FieldAccess>();
                this->writeCommand(Rehydrator::kFieldAccess_Command);
                this->write(f.base().get());
                this->writeU8(f.fieldIndex());
                this->writeU8((int8_t) f.ownerKind());
                break;
            }
            case Expression::Kind::kFunctionCall: {
                const FunctionCall& f = e->as<FunctionCall>();
                this->writeCommand(Rehydrator::kFunctionCall_Command);
                this->write(f.type());
                this->writeId(&f.function());
                this->writeU8(f.arguments().size());
                for (const auto& a : f.arguments()) {
                    this->write(a.get());
                }
                break;
            }
            case Expression::Kind::kIndex: {
                const IndexExpression& i = e->as<IndexExpression>();
                this->writeCommand(Rehydrator::kIndex_Command);
                this->write(i.base().get());
                this->write(i.index().get());
                break;
            }
            case Expression::Kind::kLiteral: {
                const Literal& l = e->as<Literal>();
                if (l.type().isFloat()) {
                    float value = l.floatValue();
                    int32_t floatBits;
                    memcpy(&floatBits, &value, sizeof(floatBits));
                    this->writeCommand(Rehydrator::kFloatLiteral_Command);
                    this->write(l.type());
                    this->writeS32(floatBits);
                } else if (l.type().isBoolean()) {
                    this->writeCommand(Rehydrator::kBoolLiteral_Command);
                    this->writeU8(l.boolValue());
                } else {
                    SkASSERT(l.type().isInteger());
                    this->writeCommand(Rehydrator::kIntLiteral_Command);
                    this->write(l.type());
                    if (l.type().isUnsigned()) {
                        this->writeU32(l.intValue());
                    } else {
                        this->writeS32(l.intValue());
                    }
                }
                break;
            }
            case Expression::Kind::kPostfix: {
                const PostfixExpression& p = e->as<PostfixExpression>();
                this->writeCommand(Rehydrator::kPostfix_Command);
                this->writeU8((int) p.getOperator().kind());
                this->write(p.operand().get());
                break;
            }
            case Expression::Kind::kPrefix: {
                const PrefixExpression& p = e->as<PrefixExpression>();
                this->writeCommand(Rehydrator::kPrefix_Command);
                this->writeU8((int) p.getOperator().kind());
                this->write(p.operand().get());
                break;
            }
            case Expression::Kind::kSetting: {
                const Setting& s = e->as<Setting>();
                this->writeCommand(Rehydrator::kSetting_Command);
                this->write(s.name());
                break;
            }
            case Expression::Kind::kSwizzle: {
                const Swizzle& s = e->as<Swizzle>();
                this->writeCommand(Rehydrator::kSwizzle_Command);
                this->write(s.base().get());
                this->writeU8(s.components().size());
                for (int c : s.components()) {
                    this->writeU8(c);
                }
                break;
            }
            case Expression::Kind::kTernary: {
                const TernaryExpression& t = e->as<TernaryExpression>();
                this->writeCommand(Rehydrator::kTernary_Command);
                this->write(t.test().get());
                this->write(t.ifTrue().get());
                this->write(t.ifFalse().get());
                break;
            }
            case Expression::Kind::kVariableReference: {
                const VariableReference& v = e->as<VariableReference>();
                this->writeCommand(Rehydrator::kVariableReference_Command);
                this->writeId(v.variable());
                this->writeU8((int8_t) v.refKind());
                break;
            }
            case Expression::Kind::kFunctionReference:
            case Expression::Kind::kMethodReference:
            case Expression::Kind::kPoison:
            case Expression::Kind::kTypeReference:
                SkDEBUGFAIL("this expression shouldn't appear in finished code");
                break;
        }
    } else {
        this->writeCommand(Rehydrator::kVoid_Command);
    }
}

void Dehydrator::write(const Statement* s) {
    if (s) {
        switch (s->kind()) {
            case Statement::Kind::kBlock: {
                const Block& b = s->as<Block>();
                this->writeCommand(Rehydrator::kBlock_Command);
                AutoDehydratorSymbolTable symbols(this, b.symbolTable());
                this->writeU8(b.children().size());
                for (const std::unique_ptr<Statement>& blockStmt : b.children()) {
                    this->write(blockStmt.get());
                }
                this->writeU8((int8_t)b.blockKind());
                break;
            }
            case Statement::Kind::kBreak:
                this->writeCommand(Rehydrator::kBreak_Command);
                break;
            case Statement::Kind::kContinue:
                this->writeCommand(Rehydrator::kContinue_Command);
                break;
            case Statement::Kind::kDiscard:
                this->writeCommand(Rehydrator::kDiscard_Command);
                break;
            case Statement::Kind::kDo: {
                const DoStatement& d = s->as<DoStatement>();
                this->writeCommand(Rehydrator::kDo_Command);
                this->write(d.statement().get());
                this->write(d.test().get());
                break;
            }
            case Statement::Kind::kExpression: {
                const ExpressionStatement& e = s->as<ExpressionStatement>();
                this->writeCommand(Rehydrator::kExpressionStatement_Command);
                this->write(e.expression().get());
                break;
            }
            case Statement::Kind::kFor: {
                const ForStatement& f = s->as<ForStatement>();
                this->writeCommand(Rehydrator::kFor_Command);
                AutoDehydratorSymbolTable symbols(this, f.symbols());
                this->write(f.initializer().get());
                this->write(f.test().get());
                this->write(f.next().get());
                this->write(f.statement().get());
                break;
            }
            case Statement::Kind::kIf: {
                const IfStatement& i = s->as<IfStatement>();
                this->writeCommand(Rehydrator::kIf_Command);
                this->writeU8(i.isStatic());
                this->write(i.test().get());
                this->write(i.ifTrue().get());
                this->write(i.ifFalse().get());
                break;
            }
            case Statement::Kind::kNop:
                this->writeCommand(Rehydrator::kNop_Command);
                break;
            case Statement::Kind::kReturn: {
                const ReturnStatement& r = s->as<ReturnStatement>();
                this->writeCommand(Rehydrator::kReturn_Command);
                this->write(r.expression().get());
                break;
            }
            case Statement::Kind::kSwitch: {
                const SwitchStatement& ss = s->as<SwitchStatement>();
                this->writeCommand(Rehydrator::kSwitch_Command);
                this->writeU8(ss.isStatic());
                AutoDehydratorSymbolTable symbols(this, ss.symbols());
                this->write(ss.value().get());
                this->writeU8(ss.cases().size());
                for (const std::unique_ptr<Statement>& stmt : ss.cases()) {
                    const SwitchCase& sc = stmt->as<SwitchCase>();
                    if (sc.isDefault()) {
                        this->writeU8(1);
                    } else {
                        this->writeU8(0);
                        this->writeS32(sc.value());
                    }
                    this->write(sc.statement().get());
                }
                break;
            }
            case Statement::Kind::kSwitchCase:
                SkDEBUGFAIL("SwitchCase statements shouldn't appear here");
                break;
            case Statement::Kind::kVarDeclaration: {
                const VarDeclaration& v = s->as<VarDeclaration>();
                this->writeCommand(Rehydrator::kVarDeclaration_Command);
                this->writeU16(this->symbolId(&v.var()));
                this->write(v.baseType());
                this->writeU8(v.arraySize());
                this->write(v.value().get());
                break;
            }
        }
    } else {
        this->writeCommand(Rehydrator::kVoid_Command);
    }
}

void Dehydrator::write(const ProgramElement& e) {
    switch (e.kind()) {
        case ProgramElement::Kind::kExtension:
            SkASSERT(false);
            break;
        case ProgramElement::Kind::kFunction: {
            const FunctionDefinition& f = e.as<FunctionDefinition>();
            this->writeCommand(Rehydrator::kFunctionDefinition_Command);
            this->writeU16(this->symbolId(&f.declaration()));
            this->write(f.body().get());
            break;
        }
        case ProgramElement::Kind::kFunctionPrototype: {
            const FunctionPrototype& f = e.as<FunctionPrototype>();
            if (!f.isBuiltin()) {
                this->writeCommand(Rehydrator::kFunctionPrototype_Command);
                this->writeU16(this->symbolId(&f.declaration()));
            }
            break;
        }
        case ProgramElement::Kind::kInterfaceBlock: {
            const InterfaceBlock& i = e.as<InterfaceBlock>();
            this->writeCommand(Rehydrator::kInterfaceBlock_Command);
            this->write(i.variable());
            this->write(i.typeName());
            this->write(i.instanceName());
            this->writeU8(i.arraySize());
            break;
        }
        case ProgramElement::Kind::kModifiers:
            SkASSERT(false);
            break;
        case ProgramElement::Kind::kStructDefinition: {
            const StructDefinition& structDef = e.as<StructDefinition>();
            this->writeCommand(Rehydrator::kStructDefinition_Command);
            this->write(structDef.type());
            break;
        }
        case ProgramElement::Kind::kGlobalVar: {
            const GlobalVarDeclaration& v = e.as<GlobalVarDeclaration>();
            this->writeCommand(Rehydrator::kGlobalVar_Command);
            this->write(v.declaration().get());
            break;
        }
    }
}

void Dehydrator::write(const std::vector<std::unique_ptr<ProgramElement>>& elements) {
    this->writeCommand(Rehydrator::kElements_Command);
    for (const auto& e : elements) {
        this->write(*e);
    }
    this->writeCommand(Rehydrator::kElementsComplete_Command);
}

void Dehydrator::write(const Program& program) {
    this->writeCommand(Rehydrator::kProgram_Command);
    this->writeU8((int)program.fConfig->fKind);
    this->writeU8((int)program.fConfig->fRequiredSkSLVersion);
    this->write(*program.fSymbols);

    // Write the elements
    this->writeCommand(Rehydrator::kElements_Command);
    for (const auto& e : program.fSharedElements) {
        this->writeCommand(Rehydrator::kSharedFunction_Command);
        const FunctionDefinition& f = e->as<FunctionDefinition>();
        const FunctionDeclaration& decl = f.declaration();
        this->writeU8(decl.parameters().size());
        for (const Variable* param : decl.parameters()) {
            this->write(*param);
        }
        this->write(f.declaration());
        this->write(*e);
    }
    for (const auto& e : program.fOwnedElements) {
        this->write(*e);
    }
    this->writeCommand(Rehydrator::kElementsComplete_Command);

    // Write the inputs
    struct KnownSkSLProgramInputs { bool useRTFlipUniform; };
    // Since it would be easy to forget to update this code in the face of Inputs changes and any
    // resulting bugs could be very subtle, assert that the struct hasn't changed:
    static_assert(sizeof(SkSL::Program::Inputs) == sizeof(KnownSkSLProgramInputs));
    this->writeU8(program.fInputs.fUseFlipRTUniform);
}

void Dehydrator::finish(OutputStream& out) {
    out.write16(Rehydrator::kVersion);
    std::string stringBuffer = fStringBuffer.str();
    std::string commandBuffer = fBody.str();
    out.write16(fStringBuffer.str().size());
    fStringBufferStart = 4;
    out.writeString(stringBuffer);
    fCommandStart = fStringBufferStart + stringBuffer.size();
    out.writeString(commandBuffer);
}

const char* Dehydrator::prefixAtOffset(size_t byte) {
    if (byte >= fCommandStart) {
        return fCommandBreaks.contains(byte - fCommandStart) ? "\n" : "";
    }
    if (byte >= fStringBufferStart) {
        return fStringBreaks.contains(byte - fStringBufferStart) ? "\n" : "";
    }
    return "";
}

} // namespace SkSL