package invoice

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

type LNbitsClient struct {
	baseURL    string
	invoiceKey string
	hc         *http.Client
}

func NewLNbits(baseURL, invoiceKey string) *LNbitsClient {
	return &LNbitsClient{
		baseURL:    strings.TrimRight(baseURL, "/"),
		invoiceKey: invoiceKey,
		hc:         &http.Client{Timeout: 15 * time.Second},
	}
}

type createReq struct {
	Out    bool   `json:"out"`
	Amount int64  `json:"amount"`
	Memo   string `json:"memo"`
	Expiry int    `json:"expiry,omitempty"`
}

type createResp struct {
	PaymentHash    string `json:"payment_hash"`
	PaymentRequest string `json:"payment_request"`
	BOLT11         string `json:"bolt11"`
}

type statusResp struct {
	Paid    bool `json:"paid"`
	Pending bool `json:"pending"`
	Details *struct {
		Pending bool `json:"pending"`
		Status  string `json:"status"`
	} `json:"details"`
}

func (c *LNbitsClient) Create(ctx context.Context, amountSats int64, memo string, expirySecs int) (string, string, error) {
	body, err := json.Marshal(createReq{Out: false, Amount: amountSats, Memo: memo, Expiry: expirySecs})
	if err != nil {
		return "", "", err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/api/v1/payments", bytes.NewReader(body))
	if err != nil {
		return "", "", err
	}
	req.Header.Set("X-Api-Key", c.invoiceKey)
	req.Header.Set("Content-Type", "application/json")
	resp, err := c.hc.Do(req)
	if err != nil {
		return "", "", fmt.Errorf("%w: %v", ErrLNbits, err)
	}
	defer resp.Body.Close()
	b, _ := io.ReadAll(resp.Body)
	if resp.StatusCode/100 != 2 {
		return "", "", fmt.Errorf("%w: %s", ErrLNbits, string(b))
	}
	var cr createResp
	if err := json.Unmarshal(b, &cr); err != nil {
		return "", "", fmt.Errorf("%w: decode: %v", ErrLNbits, err)
	}
	pr := cr.PaymentRequest
	if pr == "" {
		pr = cr.BOLT11
	}
	return cr.PaymentHash, pr, nil
}

func (c *LNbitsClient) Status(ctx context.Context, hash string) (bool, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.baseURL+"/api/v1/payments/"+hash, nil)
	if err != nil {
		return false, err
	}
	req.Header.Set("X-Api-Key", c.invoiceKey)
	resp, err := c.hc.Do(req)
	if err != nil {
		return false, fmt.Errorf("%w: %v", ErrLNbits, err)
	}
	defer resp.Body.Close()
	if resp.StatusCode == http.StatusNotFound {
		return false, nil
	}
	if resp.StatusCode/100 != 2 {
		b, _ := io.ReadAll(resp.Body)
		return false, fmt.Errorf("%w: %s", ErrLNbits, string(b))
	}
	var sr statusResp
	if err := json.NewDecoder(resp.Body).Decode(&sr); err != nil {
		return false, err
	}
	return sr.Paid, nil
}