package config

import (
	"encoding/json"
	"fmt"
	"strings"
)

// ParseChannelAccounts decodes the CHANNELS_JSON value into a per-platform list
// of ChannelAccount. The wire shape is map[platform]→[]ChannelAccount, for
// example:
//
//	{"telegram":[{"id":"conf0","config":{"bot_token":"..."},"denyUsers":["12345"]}]}
//
// An empty/blank input yields an empty (non-nil) map so a caller can iterate it
// unconditionally. A malformed JSON or a non-array account value returns an
// error so a bad config fails loudly at boot rather than silently dropping
// channels.
func ParseChannelAccounts(raw string) (map[string][]ChannelAccount, error) {
	if strings.TrimSpace(raw) == "" {
		return map[string][]ChannelAccount{}, nil
	}
	var m map[string][]ChannelAccount
	dec := json.NewDecoder(strings.NewReader(raw))
	if err := dec.Decode(&m); err != nil {
		return nil, fmt.Errorf("config: decode CHANNELS_JSON: %w", err)
	}
	// Tolerate a top-level array of accounts that all share a blank platform name
	// by normalizing a nil map to an empty one.
	if m == nil {
		return map[string][]ChannelAccount{}, nil
	}
	return m, nil
}