micro/metadata/metadata.go
2020-03-26 18:50:00 +00:00

105 lines
2.2 KiB
Go

// Package metadata is a way of defining message headers
package metadata
import (
"context"
"strings"
)
type metaKey struct{}
// Metadata is our way of representing request headers internally.
// They're used at the RPC level and translate back and forth
// from Transport headers.
type Metadata map[string]string
func (md Metadata) Get(key string) (string, bool) {
// attempt to get as is
val, ok := md[key]
if ok {
return val, ok
}
// attempt to get lower case
val, ok = md[strings.Title(key)]
return val, ok
}
// Copy makes a copy of the metadata
func Copy(md Metadata) Metadata {
cmd := make(Metadata)
for k, v := range md {
cmd[k] = v
}
return cmd
}
// Set add key with val to metadata
func Set(ctx context.Context, k, v string) context.Context {
md, ok := FromContext(ctx)
if !ok {
md = make(Metadata)
}
md[k] = v
return context.WithValue(ctx, metaKey{}, md)
}
// Get returns a single value from metadata in the context
func Get(ctx context.Context, key string) (string, bool) {
md, ok := FromContext(ctx)
if !ok {
return "", ok
}
// attempt to get as is
val, ok := md[key]
if ok {
return val, ok
}
// attempt to get lower case
val, ok = md[strings.Title(key)]
return val, ok
}
// FromContext returns metadata from the given context
func FromContext(ctx context.Context) (Metadata, bool) {
md, ok := ctx.Value(metaKey{}).(Metadata)
if !ok {
return nil, ok
}
// capitalise all values
newMD := make(map[string]string, len(md))
for k, v := range md {
newMD[strings.Title(k)] = v
}
return newMD, ok
}
// NewContext creates a new context with the given metadata
func NewContext(ctx context.Context, md Metadata) context.Context {
return context.WithValue(ctx, metaKey{}, md)
}
// MergeContext merges metadata to existing metadata, overwriting if specified
func MergeContext(ctx context.Context, patchMd Metadata, overwrite bool) context.Context {
if ctx == nil {
ctx = context.Background()
}
md, _ := ctx.Value(metaKey{}).(Metadata)
cmd := make(Metadata)
for k, v := range md {
cmd[k] = v
}
for k, v := range patchMd {
if _, ok := cmd[k]; ok && !overwrite {
// skip
} else {
cmd[k] = v
}
}
return context.WithValue(ctx, metaKey{}, cmd)
}