package fleet

import (
	"bytes"
	"context"
	"encoding/json"
	"net/http"
	"time"
)

// Markets counts the venues listed on a network's native DEX graph.
type Markets interface {
	Count(ctx context.Context, network string) (int, bool)
}

// graphHost is the explorer that serves each network's DEX graph.
var graphHost = map[string]string{
	"mainnet": "explorer.lux.network",
	"testnet": "explorer.testnet.lux.network",
	"devnet":  "explorer.devnet.lux.network",
}

// Graph reads the market count from the explorer's DEX GraphQL endpoint.
// A network whose graph is not up simply reports no count.
type Graph struct{ http *http.Client }

// NewGraph returns a market counter with a short budget — the count is a
// garnish on the overview, never a reason to hold it up.
func NewGraph() *Graph { return &Graph{http: &http.Client{Timeout: 4 * time.Second}} }

// Count returns the number of markets, and whether the graph answered.
func (g *Graph) Count(ctx context.Context, network string) (int, bool) {
	host, ok := graphHost[network]
	if !ok {
		return 0, false
	}
	body := []byte(`{"query":"{ markets { id } }"}`)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
		"https://"+host+"/v1/graph/lux/dex/graphql", bytes.NewReader(body))
	if err != nil {
		return 0, false
	}
	req.Header.Set("Content-Type", "application/json")
	resp, err := g.http.Do(req)
	if err != nil {
		return 0, false
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return 0, false
	}
	var out struct {
		Data struct {
			Markets []json.RawMessage `json:"markets"`
		} `json:"data"`
	}
	if json.NewDecoder(resp.Body).Decode(&out) != nil || out.Data.Markets == nil {
		return 0, false
	}
	return len(out.Data.Markets), true
}