lilleman
77 lines
2.3 KiB
Go
77 lines
2.3 KiB
Go
// Package fakes generates fake data from recursive, locale-specific JSON
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// templates.
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//
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// Locale data lives in JSON on disk, not in Go. Point [New] at a locale
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// directory, then generate values by category path:
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//
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// f, _ := fakes.New("./locales/sv_SE", fakes.WithSeed(42))
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// f.Fake("address") // "Storgatan 12\n234 56 Göteborg"
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// f.Fake("address.locality") // "Göteborg"
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//
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// The directory's name is the locale and must be a full tag ("sv_SE", never
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// "sv"). The JSON template format is documented in the README.
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//
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// A [Fakes] is not safe for concurrent use; create one per goroutine.
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package fakes
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import (
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crand "crypto/rand"
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"encoding/binary"
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"fmt"
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"math/rand/v2"
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"path/filepath"
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)
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// Fakes generates fake data for a single locale. Create one with [New].
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type Fakes struct {
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rand *rand.Rand
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locale string
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categories map[string]node // category name -> compiled node tree
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}
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type config struct {
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seed uint64
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seeded bool
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}
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// Option configures a [Fakes].
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type Option func(*config)
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// WithSeed makes output reproducible: two fakers with the same seed and locale
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// emit identical sequences.
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func WithSeed(seed uint64) Option {
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return func(c *config) { c.seed, c.seeded = seed, true }
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}
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// New builds a faker from a locale directory (e.g. "./locales/sv_SE"). The
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// directory's name is the locale tag and must be a full tag like "sv_SE"; each
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// JSON file in it becomes a category named after the file (address.json ->
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// "address"). It errors on a non-full tag, a missing directory, or invalid JSON.
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func New(dir string, opts ...Option) (*Fakes, error) {
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name, ok := canonicalLocale(filepath.Base(dir))
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if !ok {
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return nil, fmt.Errorf("fakes: %q is not a full locale tag like \"sv_SE\"", filepath.Base(dir))
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}
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cats, err := loadLocale(dir)
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if err != nil {
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return nil, fmt.Errorf("fakes: %s: %w", name, err)
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}
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var c config
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for _, opt := range opts {
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opt(&c)
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}
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return &Fakes{rand: newRand(c.seed, c.seeded), locale: name, categories: cats}, nil
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}
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// Locale returns the faker's canonical locale tag.
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func (f *Fakes) Locale() string { return f.locale }
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func newRand(seed uint64, seeded bool) *rand.Rand {
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if !seeded {
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var b [16]byte
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_, _ = crand.Read(b[:])
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return rand.New(rand.NewPCG(binary.LittleEndian.Uint64(b[:8]), binary.LittleEndian.Uint64(b[8:])))
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}
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return rand.New(rand.NewPCG(seed, seed^0x9e3779b97f4a7c15))
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}
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