enumer/stringer.go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build go1.5

//# Enumer [![Go Report Card](https://goreportcard.com/badge/github.com/alvaroloes/enumer)](https://goreportcard.com/report/github.com/alvaroloes/enumer) ![cover.run go](https://cover.run/go/github.com/alvaroloes/enumer.svg?tag=golang-1.10)
//Enumer is a tool to generate Go code that adds useful methods to Go enums (constants with a specific type).
//It started as a fork of [Rob Pike’s Stringer tool](https://godoc.org/golang.org/x/tools/cmd/stringer).
//
//## Generated functions and methods
//When Enumer is applied to a type, it will generate:
//
//* The following basic methods/functions:
//
//* Method `String()`: returns the string representation of the enum value. This makes the enum conform
//the `Stringer` interface, so whenever you print an enum value, you'll get the string name instead of a number.
//* Function `<Type>String(s string)`: returns the enum value from its string representation. This is useful
//when you need to read enum values from command line arguments, from a configuration file, or
//from a REST API request... In short, from those places where using the real enum value (an integer) would
//be almost meaningless or hard to trace or use by a human.
//* Function `<Type>Values()`: returns a slice with all the values of the enum
//* Method `IsA<Type>()`: returns true only if the current value is among the values of the enum. Useful for validations.
//* When the flag `json` is provided, two additional methods will be generated, `MarshalJSON()` and `UnmarshalJSON()`. These make
//the enum conform to the `json.Marshaler` and `json.Unmarshaler` interfaces. Very useful to use it in JSON APIs.
//* When the flag `text` is provided, two additional methods will be generated, `MarshalText()` and `UnmarshalText()`. These make
//the enum conform to the `encoding.TextMarshaler` and `encoding.TextUnmarshaler` interfaces.
//**Note:** If you use your enum values as keys in a map and you encode the map as _JSON_, you need this flag set to true to properly
//convert the map keys to json (strings). If not, the numeric values will be used instead
//* When the flag `yaml` is provided, two additional methods will be generated, `MarshalYAML()` and `UnmarshalYAML()`. These make
//the enum conform to the `gopkg.in/yaml.v2.Marshaler` and `gopkg.in/yaml.v2.Unmarshaler` interfaces.
//* When the flag `sql` is provided, the methods for implementing the Scanner and Valuer interfaces will be also generated.
//Useful when storing the enum in a database.
//
//For example, if we have an enum type called `Pill`,
//```go
//type Pill int
//
//const (
//	Placebo Pill = iota
//	Aspirin
//	Ibuprofen
//	Paracetamol
//	Acetaminophen = Paracetamol
//)
//```
//executing `enumer -type=Pill -json` will generate a new file with four basic method and two extra for JSON:
//```go
//func (i Pill) String() string {
//	//...
//}
//
//func PillString(s string) (Pill, error) {
//	//...
//}
//
//func PillValues() []Pill {
//	//...
//}
//
//func (i Pill) IsAPill() bool {
//	//...
//}
//
//func (i Pill) MarshalJSON() ([]byte, error) {
//	//...
//}
//
//func (i *Pill) UnmarshalJSON(data []byte) error {
//	//...
//}
//```
//From now on, we can:
//```go
//// Convert any Pill value to string
//var aspirinString string = Aspirin.String()
//// (or use it in any place where a Stringer is accepted)
//fmt.Println("I need ", Paracetamol) // Will print "I need Paracetamol"
//
//// Convert a string with the enum name to the corresponding enum value
//pill, err := PillString("Ibuprofen")
//if err != nil {
//    fmt.Println("Unrecognized pill: ", err)
//    return
//}
//// Now pill == Ibuprofen
//
//// Get all the values of the string
//allPills := PillValues()
//fmt.Println(allPills) // Will print [Placebo Aspirin Ibuprofen Paracetamol]
//
//// Check if a value belongs to the Pill enum values
//var notAPill Pill = 42
//if (notAPill.IsAPill()) {
//	fmt.Println(notAPill, "is not a value of the Pill enum")
//}
//
//// Marshal/unmarshal to/from json strings, either directly or automatically when
//// the enum is a field of a struct
//pillJSON := Aspirin.MarshalJSON()
//// Now pillJSON == `"Aspirin"`
//```
//
//The generated code is exactly the same as the Stringer tool plus the mentioned additions, so you can use
//**Enumer** where you are already using **Stringer** without any code change.
//
//## Transforming the string representation of the enum value
//
//By default, Enumer uses the same name of the enum value for generating the string representation (usually CamelCase in Go).
//
//```go
//type MyType int
//
// ...
//
//name := MyTypeValue.String() // name => "MyTypeValue"
//```
//
//Sometimes you need to use some other string representation format than CamelCase (i.e. in JSON).
//
//To transform it from CamelCase to snake_case or kebab-case, you can use the `transform` flag.
//
//For example, the command `enumer -type=MyType -json -transform=snake` would generate the following string representation:
//
//```go
//name := MyTypeValue.String() // name => "my_type_value"
//```
//**Note**: The transformation only works form CamelCase to snake_case or kebab-case, not the other way around.
//
//## How to use
//The usage of Enumer is the same as Stringer, so you can refer to the [Stringer docs](https://godoc.org/golang.org/x/tools/cmd/stringer)
//for more information.
//
//There are four boolean flags: `json`, `text`, `yaml` and `sql`. You can use any combination of them (i.e. `enumer -type=Pill -json -text`),
//
//
//For enum string representation transformation the `transform` and `trimprefix` flags
//were added (i.e. `enumer -type=MyType -json -transform=snake`).
//Possible transform values are `snake` and `kebab` for transformation to snake_case and kebab-case accordingly.
//The default value for `transform` flag is `noop` which means no transformation will be performed.
//
//If a prefix is provided via the `trimprefix` flag, it will be trimmed from the start of each name (before
//it is transformed). If a name doesn't have the prefix it will be passed unchanged.
//
//## Inspiring projects
//* [Stringer](https://godoc.org/golang.org/x/tools/cmd/stringer)
//* [jsonenums](https://github.com/campoy/jsonenums)
package main

import (
	"bytes"
	"flag"
	"fmt"
	"go/ast"
	"go/build"
	exact "go/constant"
	"go/format"
	"go/parser"
	"go/token"
	"go/types"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/pascaldekloe/name"
)

var (
	typeNames       = flag.String("type", "", "comma-separated list of type names; must be set")
	sql             = flag.Bool("sql", false, "if true, the Scanner and Valuer interface will be implemented.")
	json            = flag.Bool("json", false, "if true, json marshaling methods will be generated. Default: false")
	yaml            = flag.Bool("yaml", false, "if true, yaml marshaling methods will be generated. Default: false")
	text            = flag.Bool("text", false, "if true, text marshaling methods will be generated. Default: false")
	output          = flag.String("output", "", "output file name; default srcdir/<type>_string.go")
	transformMethod = flag.String("transform", "noop", "enum item name transformation method. Default: noop")
	trimPrefix      = flag.String("trimprefix", "", "transform each item name by removing a prefix. Default: \"\"")
)

// Usage is a replacement usage function for the flags package.
func Usage() {
	fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
	fmt.Fprintf(os.Stderr, "\tstringer [flags] -type T [directory]\n")
	fmt.Fprintf(os.Stderr, "\tstringer [flags] -type T files... # Must be a single package\n")
	fmt.Fprintf(os.Stderr, "For more information, see:\n")
	fmt.Fprintf(os.Stderr, "\thttp://godoc.org/golang.org/x/tools/cmd/stringer\n")
	fmt.Fprintf(os.Stderr, "Flags:\n")
	flag.PrintDefaults()
}

func main() {
	log.SetFlags(0)
	log.SetPrefix("enumer: ")
	flag.Usage = Usage
	flag.Parse()
	if len(*typeNames) == 0 {
		flag.Usage()
		os.Exit(2)
	}
	types := strings.Split(*typeNames, ",")

	// We accept either one directory or a list of files. Which do we have?
	args := flag.Args()
	if len(args) == 0 {
		// Default: process whole package in current directory.
		args = []string{"."}
	}

	// Parse the package once.
	var (
		dir string
		g   Generator
	)

	if len(args) == 1 && isDirectory(args[0]) {
		dir = args[0]
		g.parsePackageDir(args[0])
	} else {
		dir = filepath.Dir(args[0])
		g.parsePackageFiles(args)
	}

	// Print the header and package clause.
	g.Printf("// Code generated by \"enumer %s\"; DO NOT EDIT\n", strings.Join(os.Args[1:], " "))
	g.Printf("\n")
	g.Printf("package %s", g.pkg.name)
	g.Printf("\n")
	g.Printf("import (\n")
	g.Printf("\t\"fmt\"\n")
	if *sql {
		g.Printf("\t\"database/sql/driver\"\n")
	}
	if *json {
		g.Printf("\t\"encoding/json\"\n")
	}
	g.Printf(")\n")

	// Run generate for each type.
	for _, typeName := range types {
		g.generate(typeName, *json, *yaml, *sql, *text, *transformMethod, *trimPrefix)
	}

	// Format the output.
	src := g.format()

	// Write to file.
	outputName := *output
	if outputName == "" {
		baseName := fmt.Sprintf("%s_enumer.go", types[0])
		outputName = filepath.Join(dir, strings.ToLower(baseName))
	}
	err := ioutil.WriteFile(outputName, src, 0644)
	if err != nil {
		log.Fatalf("writing output: %s", err)
	}
}

// isDirectory reports whether the named file is a directory.
func isDirectory(name string) bool {
	info, err := os.Stat(name)
	if err != nil {
		log.Fatal(err)
	}
	return info.IsDir()
}

// Generator holds the state of the analysis. Primarily used to buffer
// the output for format.Source.
type Generator struct {
	buf bytes.Buffer // Accumulated output.
	pkg *Package     // Package we are scanning.
}

// Printf prints the string to the output
func (g *Generator) Printf(format string, args ...interface{}) {
	fmt.Fprintf(&g.buf, format, args...)
}

// File holds a single parsed file and associated data.
type File struct {
	pkg  *Package  // Package to which this file belongs.
	file *ast.File // Parsed AST.
	// These fields are reset for each type being generated.
	typeName string  // Name of the constant type.
	values   []Value // Accumulator for constant values of that type.
}

// Package holds information about a Go package
type Package struct {
	dir      string
	name     string
	defs     map[*ast.Ident]types.Object
	files    []*File
	typesPkg *types.Package
}

// parsePackageDir parses the package residing in the directory.
func (g *Generator) parsePackageDir(directory string) {
	pkg, err := build.Default.ImportDir(directory, 0)
	if err != nil {
		log.Fatalf("cannot process directory %s: %s", directory, err)
	}
	var names []string
	names = append(names, pkg.GoFiles...)
	names = append(names, pkg.CgoFiles...)
	// TODO: Need to think about constants in test files. Maybe write type_string_test.go
	// in a separate pass? For later.
	// names = append(names, pkg.TestGoFiles...) // These are also in the "foo" package.
	names = append(names, pkg.SFiles...)
	names = prefixDirectory(directory, names)
	g.parsePackage(directory, names, nil)
}

// parsePackageFiles parses the package occupying the named files.
func (g *Generator) parsePackageFiles(names []string) {
	g.parsePackage(".", names, nil)
}

// prefixDirectory places the directory name on the beginning of each name in the list.
func prefixDirectory(directory string, names []string) []string {
	if directory == "." {
		return names
	}
	ret := make([]string, len(names))
	for i, name := range names {
		ret[i] = filepath.Join(directory, name)
	}
	return ret
}

// parsePackage analyzes the single package constructed from the named files.
// If text is non-nil, it is a string to be used instead of the content of the file,
// to be used for testing. parsePackage exits if there is an error.
func (g *Generator) parsePackage(directory string, names []string, text interface{}) {
	var files []*File
	var astFiles []*ast.File
	g.pkg = new(Package)
	fs := token.NewFileSet()
	for _, name := range names {
		if !strings.HasSuffix(name, ".go") {
			continue
		}
		parsedFile, err := parser.ParseFile(fs, name, text, 0)
		if err != nil {
			log.Fatalf("parsing package: %s: %s", name, err)
		}
		astFiles = append(astFiles, parsedFile)
		files = append(files, &File{
			file: parsedFile,
			pkg:  g.pkg,
		})
	}
	if len(astFiles) == 0 {
		log.Fatalf("%s: no buildable Go files", directory)
	}
	g.pkg.name = astFiles[0].Name.Name
	g.pkg.files = files
	g.pkg.dir = directory
	// Type check the package.
	g.pkg.check(fs, astFiles)
}

// check type-checks the package. The package must be OK to proceed.
func (pkg *Package) check(fs *token.FileSet, astFiles []*ast.File) {
	pkg.defs = make(map[*ast.Ident]types.Object)
	config := types.Config{Importer: defaultImporter(), FakeImportC: true}
	info := &types.Info{
		Defs: pkg.defs,
	}
	typesPkg, err := config.Check(pkg.dir, fs, astFiles, info)
	if err != nil {
		log.Fatalf("checking package: %s", err)
	}
	pkg.typesPkg = typesPkg
}

func (g *Generator) transformValueNames(values []Value, transformMethod string) {
	var sep rune
	switch transformMethod {
	case "snake":
		sep = '_'
	case "kebab":
		sep = '-'
	default:
		return
	}

	for i := range values {
		values[i].name = strings.ToLower(name.Delimit(values[i].name, sep))
	}
}

// trimValueNames removes a prefix from each name
func (g *Generator) trimValueNames(values []Value, prefix string) {
	for i := range values {
		values[i].name = strings.TrimPrefix(values[i].name, prefix)
	}
}

// generate produces the String method for the named type.
func (g *Generator) generate(typeName string, includeJSON, includeYAML, includeSQL, includeText bool, transformMethod string, trimPrefix string) {
	values := make([]Value, 0, 100)
	for _, file := range g.pkg.files {
		// Set the state for this run of the walker.
		file.typeName = typeName
		file.values = nil
		if file.file != nil {
			ast.Inspect(file.file, file.genDecl)
			values = append(values, file.values...)
		}
	}

	if len(values) == 0 {
		log.Fatalf("no values defined for type %s", typeName)
	}

	g.trimValueNames(values, trimPrefix)

	g.transformValueNames(values, transformMethod)

	runs := splitIntoRuns(values)
	// The decision of which pattern to use depends on the number of
	// runs in the numbers. If there's only one, it's easy. For more than
	// one, there's a tradeoff between complexity and size of the data
	// and code vs. the simplicity of a map. A map takes more space,
	// but so does the code. The decision here (crossover at 10) is
	// arbitrary, but considers that for large numbers of runs the cost
	// of the linear scan in the switch might become important, and
	// rather than use yet another algorithm such as binary search,
	// we punt and use a map. In any case, the likelihood of a map
	// being necessary for any realistic example other than bitmasks
	// is very low. And bitmasks probably deserve their own analysis,
	// to be done some other day.
	const runsThreshold = 10
	switch {
	case len(runs) == 1:
		g.buildOneRun(runs, typeName)
	case len(runs) <= runsThreshold:
		g.buildMultipleRuns(runs, typeName)
	default:
		g.buildMap(runs, typeName)
	}

	g.buildBasicExtras(runs, typeName, runsThreshold)
	if includeJSON {
		g.buildJSONMethods(runs, typeName, runsThreshold)
	}
	if includeText {
		g.buildTextMethods(runs, typeName, runsThreshold)
	}
	if includeYAML {
		g.buildYAMLMethods(runs, typeName, runsThreshold)
	}
	if includeSQL {
		g.addValueAndScanMethod(typeName)
	}
}

// splitIntoRuns breaks the values into runs of contiguous sequences.
// For example, given 1,2,3,5,6,7 it returns {1,2,3},{5,6,7}.
// The input slice is known to be non-empty.
func splitIntoRuns(values []Value) [][]Value {
	// We use stable sort so the lexically first name is chosen for equal elements.
	sort.Stable(byValue(values))
	// Remove duplicates. Stable sort has put the one we want to print first,
	// so use that one. The String method won't care about which named constant
	// was the argument, so the first name for the given value is the only one to keep.
	// We need to do this because identical values would cause the switch or map
	// to fail to compile.
	j := 1
	for i := 1; i < len(values); i++ {
		if values[i].value != values[i-1].value {
			values[j] = values[i]
			j++
		}
	}
	values = values[:j]
	runs := make([][]Value, 0, 10)
	for len(values) > 0 {
		// One contiguous sequence per outer loop.
		i := 1
		for i < len(values) && values[i].value == values[i-1].value+1 {
			i++
		}
		runs = append(runs, values[:i])
		values = values[i:]
	}
	return runs
}

// format returns the gofmt-ed contents of the Generator's buffer.
func (g *Generator) format() []byte {
	src, err := format.Source(g.buf.Bytes())
	if err != nil {
		// Should never happen, but can arise when developing this code.
		// The user can compile the output to see the error.
		log.Printf("warning: internal error: invalid Go generated: %s", err)
		log.Printf("warning: compile the package to analyze the error")
		return g.buf.Bytes()
	}
	return src
}

// Value represents a declared constant.
type Value struct {
	name string // The name of the constant after transformation (i.e. camel case => snake case)
	// The value is stored as a bit pattern alone. The boolean tells us
	// whether to interpret it as an int64 or a uint64; the only place
	// this matters is when sorting.
	// Much of the time the str field is all we need; it is printed
	// by Value.String.
	value  uint64 // Will be converted to int64 when needed.
	signed bool   // Whether the constant is a signed type.
	str    string // The string representation given by the "go/exact" package.
}

func (v *Value) String() string {
	return v.str
}

// byValue lets us sort the constants into increasing order.
// We take care in the Less method to sort in signed or unsigned order,
// as appropriate.
type byValue []Value

func (b byValue) Len() int      { return len(b) }
func (b byValue) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
func (b byValue) Less(i, j int) bool {
	if b[i].signed {
		return int64(b[i].value) < int64(b[j].value)
	}
	return b[i].value < b[j].value
}

// genDecl processes one declaration clause.
func (f *File) genDecl(node ast.Node) bool {
	decl, ok := node.(*ast.GenDecl)
	if !ok || decl.Tok != token.CONST {
		// We only care about const declarations.
		return true
	}
	// The name of the type of the constants we are declaring.
	// Can change if this is a multi-element declaration.
	typ := ""
	// Loop over the elements of the declaration. Each element is a ValueSpec:
	// a list of names possibly followed by a type, possibly followed by values.
	// If the type and value are both missing, we carry down the type (and value,
	// but the "go/types" package takes care of that).
	for _, spec := range decl.Specs {
		vspec := spec.(*ast.ValueSpec) // Guaranteed to succeed as this is CONST.
		if vspec.Type == nil && len(vspec.Values) > 0 {
			// "X = 1". With no type but a value, the constant is untyped.
			// Skip this vspec and reset the remembered type.
			typ = ""
			continue
		}
		if vspec.Type != nil {
			// "X T". We have a type. Remember it.
			ident, ok := vspec.Type.(*ast.Ident)
			if !ok {
				continue
			}
			typ = ident.Name
		}
		if typ != f.typeName {
			// This is not the type we're looking for.
			continue
		}
		// We now have a list of names (from one line of source code) all being
		// declared with the desired type.
		// Grab their names and actual values and store them in f.values.
		for _, name := range vspec.Names {
			if name.Name == "_" {
				continue
			}
			// This dance lets the type checker find the values for us. It's a
			// bit tricky: look up the object declared by the name, find its
			// types.Const, and extract its value.
			obj, ok := f.pkg.defs[name]
			if !ok {
				log.Fatalf("no value for constant %s", name)
			}
			info := obj.Type().Underlying().(*types.Basic).Info()
			if info&types.IsInteger == 0 {
				log.Fatalf("can't handle non-integer constant type %s", typ)
			}
			value := obj.(*types.Const).Val() // Guaranteed to succeed as this is CONST.
			if value.Kind() != exact.Int {
				log.Fatalf("can't happen: constant is not an integer %s", name)
			}
			i64, isInt := exact.Int64Val(value)
			u64, isUint := exact.Uint64Val(value)
			if !isInt && !isUint {
				log.Fatalf("internal error: value of %s is not an integer: %s", name, value.String())
			}
			if !isInt {
				u64 = uint64(i64)
			}
			v := Value{
				name:   name.Name,
				value:  u64,
				signed: info&types.IsUnsigned == 0,
				str:    value.String(),
			}
			f.values = append(f.values, v)
		}
	}
	return false
}

// Helpers

// usize returns the number of bits of the smallest unsigned integer
// type that will hold n. Used to create the smallest possible slice of
// integers to use as indexes into the concatenated strings.
func usize(n int) int {
	switch {
	case n < 1<<8:
		return 8
	case n < 1<<16:
		return 16
	default:
		// 2^32 is enough constants for anyone.
		return 32
	}
}

// declareIndexAndNameVars declares the index slices and concatenated names
// strings representing the runs of values.
func (g *Generator) declareIndexAndNameVars(runs [][]Value, typeName string) {
	var indexes, names []string
	for i, run := range runs {
		index, name := g.createIndexAndNameDecl(run, typeName, fmt.Sprintf("_%d", i))
		indexes = append(indexes, index)
		names = append(names, name)
	}
	g.Printf("const (\n")
	for _, name := range names {
		g.Printf("\t%s\n", name)
	}
	g.Printf(")\n\n")
	g.Printf("var (")
	for _, index := range indexes {
		g.Printf("\t%s\n", index)
	}
	g.Printf(")\n\n")
}

// declareIndexAndNameVar is the single-run version of declareIndexAndNameVars
func (g *Generator) declareIndexAndNameVar(run []Value, typeName string) {
	index, name := g.createIndexAndNameDecl(run, typeName, "")
	g.Printf("const %s\n", name)
	g.Printf("var %s\n", index)
}

// createIndexAndNameDecl returns the pair of declarations for the run. The caller will add "const" and "var".
func (g *Generator) createIndexAndNameDecl(run []Value, typeName string, suffix string) (string, string) {
	b := new(bytes.Buffer)
	indexes := make([]int, len(run))
	for i := range run {
		b.WriteString(run[i].name)
		indexes[i] = b.Len()
	}
	nameConst := fmt.Sprintf("_%sName%s = %q", typeName, suffix, b.String())
	nameLen := b.Len()
	b.Reset()
	fmt.Fprintf(b, "_%sIndex%s = [...]uint%d{0, ", typeName, suffix, usize(nameLen))
	for i, v := range indexes {
		if i > 0 {
			fmt.Fprintf(b, ", ")
		}
		fmt.Fprintf(b, "%d", v)
	}
	fmt.Fprintf(b, "}")
	return b.String(), nameConst
}

// declareNameVars declares the concatenated names string representing all the values in the runs.
func (g *Generator) declareNameVars(runs [][]Value, typeName string, suffix string) {
	g.Printf("const _%sName%s = \"", typeName, suffix)
	for _, run := range runs {
		for i := range run {
			g.Printf("%s", run[i].name)
		}
	}
	g.Printf("\"\n")
}

// buildOneRun generates the variables and String method for a single run of contiguous values.
func (g *Generator) buildOneRun(runs [][]Value, typeName string) {
	values := runs[0]
	g.Printf("\n")
	g.declareIndexAndNameVar(values, typeName)
	// The generated code is simple enough to write as a Printf format.
	lessThanZero := ""
	if values[0].signed {
		lessThanZero = "i < 0 || "
	}
	if values[0].value == 0 { // Signed or unsigned, 0 is still 0.
		g.Printf(stringOneRun, typeName, usize(len(values)), lessThanZero)
	} else {
		g.Printf(stringOneRunWithOffset, typeName, values[0].String(), usize(len(values)), lessThanZero)
	}
}

// Arguments to format are:
//	[1]: type name
//	[2]: size of index element (8 for uint8 etc.)
//	[3]: less than zero check (for signed types)
const stringOneRun = `func (i %[1]s) String() string {
	if %[3]si >= %[1]s(len(_%[1]sIndex)-1) {
		return fmt.Sprintf("%[1]s(%%d)", i)
	}
	return _%[1]sName[_%[1]sIndex[i]:_%[1]sIndex[i+1]]
}
`

// Arguments to format are:
//	[1]: type name
//	[2]: lowest defined value for type, as a string
//	[3]: size of index element (8 for uint8 etc.)
//	[4]: less than zero check (for signed types)
/*
 */
const stringOneRunWithOffset = `func (i %[1]s) String() string {
	i -= %[2]s
	if %[4]si >= %[1]s(len(_%[1]sIndex)-1) {
		return fmt.Sprintf("%[1]s(%%d)", i + %[2]s)
	}
	return _%[1]sName[_%[1]sIndex[i] : _%[1]sIndex[i+1]]
}
`

// buildMultipleRuns generates the variables and String method for multiple runs of contiguous values.
// For this pattern, a single Printf format won't do.
func (g *Generator) buildMultipleRuns(runs [][]Value, typeName string) {
	g.Printf("\n")
	g.declareIndexAndNameVars(runs, typeName)
	g.Printf("func (i %s) String() string {\n", typeName)
	g.Printf("\tswitch {\n")
	for i, values := range runs {
		if len(values) == 1 {
			g.Printf("\tcase i == %s:\n", &values[0])
			g.Printf("\t\treturn _%sName_%d\n", typeName, i)
			continue
		}
		g.Printf("\tcase %s <= i && i <= %s:\n", &values[0], &values[len(values)-1])
		if values[0].value != 0 {
			g.Printf("\t\ti -= %s\n", &values[0])
		}
		g.Printf("\t\treturn _%sName_%d[_%sIndex_%d[i]:_%sIndex_%d[i+1]]\n",
			typeName, i, typeName, i, typeName, i)
	}
	g.Printf("\tdefault:\n")
	g.Printf("\t\treturn fmt.Sprintf(\"%s(%%d)\", i)\n", typeName)
	g.Printf("\t}\n")
	g.Printf("}\n")
}

// buildMap handles the case where the space is so sparse a map is a reasonable fallback.
// It's a rare situation but has simple code.
func (g *Generator) buildMap(runs [][]Value, typeName string) {
	g.Printf("\n")
	g.declareNameVars(runs, typeName, "")
	g.Printf("\nvar _%sMap = map[%s]string{\n", typeName, typeName)
	n := 0
	for _, values := range runs {
		for _, value := range values {
			g.Printf("\t%s: _%sName[%d:%d],\n", &value, typeName, n, n+len(value.name))
			n += len(value.name)
		}
	}
	g.Printf("}\n\n")
	g.Printf(stringMap, typeName)
}

// Argument to format is the type name.
const stringMap = `func (i %[1]s) String() string {
	if str, ok := _%[1]sMap[i]; ok {
		return str
	}
	return fmt.Sprintf("%[1]s(%%d)", i)
}
`