package verifyer

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"strings"
	"time"

	"slices"

	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
)

// esplora is a client for the Esplora API, which provides access to Bitcoin
// blockchain data.
type esplora struct {
	httpClient *http.Client
	baseURL    string
}

func NewEsploraClient(url string, timeout time.Duration) Bitcoin {
	url = strings.TrimSuffix(url, "/")

	h := &http.Client{
		Timeout: timeout,
	}

	return esplora{h, url}
}

func (e esplora) GetBlockHash(height int64) (*chainhash.Hash, error) {
	resp, err := e.httpClient.Get(e.baseURL + "/block-height/" + strconv.FormatInt(height, 10))
	if err != nil {
		return nil, fmt.Errorf("failed to get block hash: %w", err)
	}
	defer resp.Body.Close()

	hexb, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read block hash: %w", err)
	}

	hash, err := hex.DecodeString(string(hexb))
	if err != nil {
		return nil, fmt.Errorf("failed to decode block hash: %w", err)
	}
	if len(hash) != chainhash.HashSize {
		return nil, fmt.Errorf("got block hash (%x) of invalid size (expected %d)", hash, chainhash.HashSize)
	}

	slices.Reverse(hash)
	var chash chainhash.Hash
	copy(chash[:], hash)
	return &chash, nil
}

func (e esplora) GetBlockHeader(hash *chainhash.Hash) (*wire.BlockHeader, error) {
	resp, err := e.httpClient.Get(fmt.Sprintf("%s/block/%s/header", e.baseURL, hash.String()))
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	hexb, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	headerHash, err := hex.DecodeString(string(hexb))
	if err != nil {
		return nil, err
	}

	header := &wire.BlockHeader{}
	if err := header.BtcDecode(bytes.NewBuffer(headerHash), 0, 0); err != nil {
		return nil, err
	}

	return header, nil
}