package ratelimit

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

const usageURL = "https://api.anthropic.com/api/oauth/usage"

type RateLimit struct {
	Utilization *float64 `json:"utilization"` // 0-100
	ResetsAt    *string  `json:"resets_at"`   // ISO 8601
}

type ExtraUsage struct {
	IsEnabled   bool     `json:"is_enabled"`
	MonthlyLimit *float64 `json:"monthly_limit"`
	UsedCredits  *float64 `json:"used_credits"`
	Utilization  *float64 `json:"utilization"`
}

type UsageResponse struct {
	FiveHour     *RateLimit  `json:"five_hour"`
	SevenDay     *RateLimit  `json:"seven_day"`
	SevenDaySonnet *RateLimit `json:"seven_day_sonnet"`
	ExtraUsage   *ExtraUsage `json:"extra_usage"`
}

func fetchUsage(ctx context.Context, token string) (*UsageResponse, error) {
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, http.MethodGet, usageURL, nil)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("Authorization", "Bearer "+token)
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("anthropic-beta", "oauth-2025-04-20")
	req.Header.Set("User-Agent", "claude-cli/2.1.92")

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

	body, _ := io.ReadAll(resp.Body)
	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("usage returned %d: %s", resp.StatusCode, string(body))
	}

	var usage UsageResponse
	if err := json.Unmarshal(body, &usage); err != nil {
		return nil, fmt.Errorf("decode: %w", err)
	}
	return &usage, nil
}