go-extractor/sites/polymarket/api.go

package polymarket

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"
)

const (
	defaultGammaBaseURL = "https://gamma-api.polymarket.com"
)

// stringOrArray handles Polymarket's inconsistent JSON encoding where fields
// can be either a JSON array or a stringified JSON array (e.g. "[\"Yes\",\"No\"]").
type stringOrArray []string

func (s *stringOrArray) UnmarshalJSON(data []byte) error {
	// Try as regular array first
	var arr []string
	if err := json.Unmarshal(data, &arr); err == nil {
		*s = arr
		return nil
	}

	// Try as stringified array
	var str string
	if err := json.Unmarshal(data, &str); err == nil {
		if err := json.Unmarshal([]byte(str), &arr); err == nil {
			*s = arr
			return nil
		}
	}

	*s = nil
	return nil
}

// floatOrArray handles the same pattern for numeric arrays.
type floatOrArray []float64

func (f *floatOrArray) UnmarshalJSON(data []byte) error {
	// Try as regular array first
	var arr []float64
	if err := json.Unmarshal(data, &arr); err == nil {
		*f = arr
		return nil
	}

	// Try as array of strings
	var strArr []string
	if err := json.Unmarshal(data, &strArr); err == nil {
		result := make([]float64, 0, len(strArr))
		for _, s := range strArr {
			v, err := strconv.ParseFloat(s, 64)
			if err != nil {
				return fmt.Errorf("parsing price %q: %w", s, err)
			}
			result = append(result, v)
		}
		*f = result
		return nil
	}

	// Try as stringified array of strings
	var str string
	if err := json.Unmarshal(data, &str); err == nil {
		if err := json.Unmarshal([]byte(str), &strArr); err == nil {
			result := make([]float64, 0, len(strArr))
			for _, s := range strArr {
				v, err := strconv.ParseFloat(s, 64)
				if err != nil {
					return fmt.Errorf("parsing price %q: %w", s, err)
				}
				result = append(result, v)
			}
			*f = result
			return nil
		}
	}

	*f = nil
	return nil
}

// apiMarket is the JSON shape returned by the Gamma API for a market.
type apiMarket struct {
	ID               string       `json:"id"`
	Question         string       `json:"question"`
	Slug             string       `json:"slug"`
	Outcomes         stringOrArray `json:"outcomes"`
	OutcomePrices    floatOrArray  `json:"outcomePrices"`
	Volume           flexFloat    `json:"volume"`
	Volume24hr       float64      `json:"volume24hr"`
	LiquidityClob    float64      `json:"liquidityClob"`
	EndDate          string       `json:"endDate"`
	Active           bool         `json:"active"`
	Closed           bool         `json:"closed"`
	BestBid          float64      `json:"bestBid"`
	BestAsk          float64      `json:"bestAsk"`
	LastTradePrice   float64      `json:"lastTradePrice"`
	Description      string       `json:"description"`
	GroupItemTitle   string       `json:"groupItemTitle"`
}

// flexFloat handles volume fields that are sometimes strings, sometimes numbers.
type flexFloat float64

func (f *flexFloat) UnmarshalJSON(data []byte) error {
	var num float64
	if err := json.Unmarshal(data, &num); err == nil {
		*f = flexFloat(num)
		return nil
	}

	var str string
	if err := json.Unmarshal(data, &str); err == nil {
		v, err := strconv.ParseFloat(str, 64)
		if err != nil {
			*f = 0
			return nil
		}
		*f = flexFloat(v)
		return nil
	}

	*f = 0
	return nil
}

// apiEvent is the JSON shape returned by the Gamma API for an event.
type apiEvent struct {
	ID          string      `json:"id"`
	Title       string      `json:"title"`
	Slug        string      `json:"slug"`
	Description string      `json:"description"`
	Markets     []apiMarket `json:"markets"`
	Volume      float64     `json:"volume"`
	Volume24hr  float64     `json:"volume24hr"`
	Liquidity   float64     `json:"liquidity"`
	Active      bool        `json:"active"`
	Closed      bool        `json:"closed"`
}

// apiSearchResponse is the JSON shape returned by the public-search endpoint.
type apiSearchResponse struct {
	Events []apiEvent `json:"events"`
}

func apiMarketToMarket(m apiMarket) Market {
	return Market{
		ID:            m.ID,
		Question:      m.Question,
		Slug:          m.Slug,
		Outcomes:      []string(m.Outcomes),
		OutcomePrices: []float64(m.OutcomePrices),
		Volume:        float64(m.Volume),
		Volume24h:     m.Volume24hr,
		Liquidity:     m.LiquidityClob,
		EndDate:       m.EndDate,
		Active:        m.Active,
		Closed:        m.Closed,
		BestBid:       m.BestBid,
		BestAsk:       m.BestAsk,
		LastPrice:     m.LastTradePrice,
		Description:   m.Description,
	}
}

func apiEventToEvent(e apiEvent) Event {
	markets := make([]Market, 0, len(e.Markets))
	for _, m := range e.Markets {
		markets = append(markets, apiMarketToMarket(m))
	}

	return Event{
		ID:          e.ID,
		Title:       e.Title,
		Slug:        e.Slug,
		Description: e.Description,
		Markets:     markets,
		Volume:      e.Volume,
		Volume24h:   e.Volume24hr,
		Liquidity:   e.Liquidity,
		Active:      e.Active,
		Closed:      e.Closed,
	}
}

func (c Config) doGet(ctx context.Context, endpoint string) ([]byte, error) {
	base := c.BaseURL
	if base == "" {
		base = defaultGammaBaseURL
	}

	reqURL := base + endpoint

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
	if err != nil {
		return nil, fmt.Errorf("creating request: %w", err)
	}
	req.Header.Set("Accept", "application/json")

	client := c.HTTPClient
	if client == nil {
		client = http.DefaultClient
	}

	resp, err := client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("executing request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("reading response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API returned status %d: %s", resp.StatusCode, string(body))
	}

	return body, nil
}

func (c Config) searchAPI(ctx context.Context, query string) ([]Event, error) {
	endpoint := "/public-search?q=" + url.QueryEscape(query)

	body, err := c.doGet(ctx, endpoint)
	if err != nil {
		return nil, fmt.Errorf("searching: %w", err)
	}

	var resp apiSearchResponse
	if err := json.Unmarshal(body, &resp); err != nil {
		return nil, fmt.Errorf("parsing search response: %w", err)
	}

	events := make([]Event, 0, len(resp.Events))
	for _, e := range resp.Events {
		events = append(events, apiEventToEvent(e))
	}

	return events, nil
}

func (c Config) getEventBySlug(ctx context.Context, slug string) (*Event, error) {
	body, err := c.doGet(ctx, "/events/slug/"+url.PathEscape(slug))
	if err != nil {
		return nil, fmt.Errorf("getting event: %w", err)
	}

	var raw apiEvent
	if err := json.Unmarshal(body, &raw); err != nil {
		return nil, fmt.Errorf("parsing event: %w", err)
	}

	ev := apiEventToEvent(raw)
	return &ev, nil
}

func (c Config) getEventByID(ctx context.Context, id string) (*Event, error) {
	body, err := c.doGet(ctx, "/events/"+url.PathEscape(id))
	if err != nil {
		return nil, fmt.Errorf("getting event: %w", err)
	}

	var raw apiEvent
	if err := json.Unmarshal(body, &raw); err != nil {
		return nil, fmt.Errorf("parsing event: %w", err)
	}

	ev := apiEventToEvent(raw)
	return &ev, nil
}

func (c Config) getMarketBySlug(ctx context.Context, slug string) (*Market, error) {
	body, err := c.doGet(ctx, "/markets/slug/"+url.PathEscape(slug))
	if err != nil {
		return nil, fmt.Errorf("getting market: %w", err)
	}

	var raw apiMarket
	if err := json.Unmarshal(body, &raw); err != nil {
		return nil, fmt.Errorf("parsing market: %w", err)
	}

	m := apiMarketToMarket(raw)
	return &m, nil
}

// parsePolymarketURL extracts the type ("event" or "market") and slug from a Polymarket URL.
// Supported formats:
//   - https://polymarket.com/event/<slug>
//   - https://polymarket.com/event/<event-slug>/<market-slug>
func parsePolymarketURL(rawURL string) (urlType, slug, marketSlug string, err error) {
	u, err := url.Parse(rawURL)
	if err != nil {
		return "", "", "", fmt.Errorf("parsing URL: %w", err)
	}

	host := strings.TrimPrefix(u.Host, "www.")
	if host != "polymarket.com" {
		return "", "", "", fmt.Errorf("not a Polymarket URL: %s", rawURL)
	}

	parts := strings.Split(strings.Trim(u.Path, "/"), "/")
	if len(parts) < 2 {
		return "", "", "", fmt.Errorf("invalid Polymarket URL path: %s", u.Path)
	}

	switch parts[0] {
	case "event":
		if len(parts) >= 3 {
			return "event", parts[1], parts[2], nil
		}
		return "event", parts[1], "", nil
	default:
		return "", "", "", fmt.Errorf("unsupported Polymarket URL type: %s", parts[0])
	}
}