//go:build exclude

// TODO need compare with micro metadata
package metadata

import (
	"context"
	"fmt"
	"strings"
)

// DecodeKeyValue returns k, v, nil.
//
// Deprecated: use k and v directly instead.
func DecodeKeyValue(k, v string) (string, string, error) {
	return k, v, nil
}

// MD is a mapping from metadata keys to values. Users should use the following
// two convenience functions New and Pairs to generate MD.
type MD map[string]string

// New creates an MD from a given key-value map.
//
// Only the following ASCII characters are allowed in keys:
//   - digits: 0-9
//   - uppercase letters: A-Z (normalized to lower)
//   - lowercase letters: a-z
//   - special characters: -_.
//
// Uppercase letters are automatically converted to lowercase.
//
// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
// result in errors if set in metadata.
func New(m map[string]string) MD {
	md := make(MD, len(m))
	for k, val := range m {
		key := strings.ToLower(k)
		md[key] = val
	}
	return md
}

// Pairs returns an MD formed by the mapping of key, value ...
// Pairs panics if len(kv) is odd.
//
// Only the following ASCII characters are allowed in keys:
//   - digits: 0-9
//   - uppercase letters: A-Z (normalized to lower)
//   - lowercase letters: a-z
//   - special characters: -_.
//
// Uppercase letters are automatically converted to lowercase.
//
// Keys beginning with "grpc-" are reserved for grpc-internal use only and may
// result in errors if set in metadata.
func Pairs(kv ...string) MD {
	if len(kv)%2 == 1 {
		panic(fmt.Sprintf("metadata: Pairs got the odd number of input pairs for metadata: %d", len(kv)))
	}
	md := make(MD, len(kv)/2)
	for i := 0; i < len(kv); i += 2 {
		key := strings.ToLower(kv[i])
		md[key] = kv[i+1]
	}
	return md
}

// Len returns the number of items in md.
func (md MD) Len() int {
	return len(md)
}

// Copy returns a copy of md.
func (md MD) Copy() MD {
	out := make(MD, len(md))
	for k, v := range md {
		out[k] = v
	}
	return out
}

// Get obtains the values for a given key.
//
// k is converted to lowercase before searching in md.
func (md MD) Get(k string) string {
	k = strings.ToLower(k)
	return md[k]
}

// Set sets the value of a given key with a slice of values.
//
// k is converted to lowercase before storing in md.
func (md MD) Set(k string, vals string) {
	if len(vals) == 0 {
		return
	}
	k = strings.ToLower(k)
	md[k] = vals
}

// Append adds the values to key k, not overwriting what was already stored at
// that key.
//
// k is converted to lowercase before storing in md.
func (md MD) Append(k string, vals string) {
	if len(vals) == 0 {
		return
	}
	k = strings.ToLower(k)
	md[k] = vals
}

// Delete removes the values for a given key k which is converted to lowercase
// before removing it from md.
func (md MD) Delete(k string) {
	k = strings.ToLower(k)
	delete(md, k)
}

// Join joins any number of mds into a single MD.
//
// The order of values for each key is determined by the order in which the mds
// containing those values are presented to Join.
func Join(mds ...MD) MD {
	out := MD{}
	for _, md := range mds {
		for k, v := range md {
			out[k] = v
		}
	}
	return out
}

type mdIncomingKey struct{}
type mdOutgoingKey struct{}

// NewIncomingContext creates a new context with incoming md attached. md must
// not be modified after calling this function.
func NewIncomingContext(ctx context.Context, md MD) context.Context {
	return context.WithValue(ctx, mdIncomingKey{}, md)
}

// NewOutgoingContext creates a new context with outgoing md attached. If used
// in conjunction with AppendToOutgoingContext, NewOutgoingContext will
// overwrite any previously-appended metadata. md must not be modified after
// calling this function.
func NewOutgoingContext(ctx context.Context, md MD) context.Context {
	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md})
}

// AppendToOutgoingContext returns a new context with the provided kv merged
// with any existing metadata in the context. Please refer to the documentation
// of Pairs for a description of kv.
func AppendToOutgoingContext(ctx context.Context, kv ...string) context.Context {
	if len(kv)%2 == 1 {
		panic(fmt.Sprintf("metadata: AppendToOutgoingContext got an odd number of input pairs for metadata: %d", len(kv)))
	}
	md, _ := ctx.Value(mdOutgoingKey{}).(rawMD)

	kvCopy := make([]string, 0, len(kv))
	for i := 0; i < len(kv); i += 2 {
		kvCopy = append(kvCopy, strings.ToLower(kv[i]), kv[i+1])
	}

	return context.WithValue(ctx, mdOutgoingKey{}, rawMD{md: md.md})
}

// FromIncomingContext returns the incoming metadata in ctx if it exists.
//
// All keys in the returned MD are lowercase.
func FromIncomingContext(ctx context.Context) (MD, bool) {
	md, ok := ctx.Value(mdIncomingKey{}).(MD)
	if !ok {
		return nil, false
	}
	out := make(MD, len(md))
	for k, v := range md {
		// We need to manually convert all keys to lower case, because MD is a
		// map, and there's no guarantee that the MD attached to the context is
		// created using our helper functions.
		key := strings.ToLower(k)
		out[key] = v
	}
	return out, true
}

// fromOutgoingContextRaw returns the un-merged, intermediary contents of rawMD.
//
// Remember to perform strings.ToLower on the keys, for both the returned MD (MD
// is a map, there's no guarantee it's created using our helper functions) and
// the extra kv pairs (AppendToOutgoingContext doesn't turn them into
// lowercase).
func fromOutgoingContextRaw(ctx context.Context) (MD, bool) {
	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
	if !ok {
		return nil, false
	}

	return raw.md, true
}

// FromOutgoingContext returns the outgoing metadata in ctx if it exists.
//
// All keys in the returned MD are lowercase.
func FromOutgoingContext(ctx context.Context) (MD, bool) {
	raw, ok := ctx.Value(mdOutgoingKey{}).(rawMD)
	if !ok {
		return nil, false
	}

	out := make(MD, len(raw.md))
	for k, v := range raw.md {
		// We need to manually convert all keys to lower case, because MD is a
		// map, and there's no guarantee that the MD attached to the context is
		// created using our helper functions.
		key := strings.ToLower(k)
		out[key] = v
	}

	return out, ok
}

type rawMD struct {
	md MD
}