package payment

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/xml"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"gitea.futuresens.co.uk/futuresens/hardlink/db"
	"gitea.futuresens.co.uk/futuresens/hardlink/types"
	log "github.com/sirupsen/logrus"
)

const (
	httpTimeout = 120 * time.Second
)

/* ==============================
   Public Entry Point (LEGACY)
   ============================== */

func ReleasePreauthorizations(database *sql.DB) error {
	ctx := context.Background()
	now := time.Now().UTC()
	client := &http.Client{Timeout: httpTimeout}

	preauths, err := fetchDuePreauths(ctx, database, now)
	if err != nil {
		return err
	}

	if len(preauths) == 0 {
		log.Info("No preauthorizations due for release")
		return nil
	} else {
		log.Infof("%d preauthorizations due for release", len(preauths))
	}

	var failed []string
	var completed int
	for _, p := range preauths {
		if err := handlePreauthRelease(ctx, database, client, p, now); err != nil {
			log.Errorf("Preauth %s failed: %v", p.TxnReference, err)
			failed = append(failed, p.TxnReference)
		}
		completed++
	}
	log.Infof("Preauth release completed: %d processed, %d failed", completed, len(failed))

	if len(failed) > 0 {
		return fmt.Errorf("preauth release incomplete, failed refs: %s", strings.Join(failed, ", "))
	}

	return nil
}

/* ==============================
   Core Business Logic
   ============================== */

func handlePreauthRelease(
	ctx context.Context,
	dbConn *sql.DB,
	client *http.Client,
	preauth types.PreauthRec,
	now time.Time,
) error {

	ref := preauth.TxnReference
	log.Infof("Evaluating preauth %s", ref)

	info, err := fetchTransactionInfo(ctx, client, ref)
	if err != nil {
		return err
	}

	// If already voided or declined → mark released
	if isAlreadyReleased(info) {
		return markReleased(ctx, dbConn, ref, now)
	}

	// Only void approved + uncommitted
	if !isVoidable(info) {
		log.Infof("Preauth %s not eligible for void (res=%s state=%s)",
			ref, info.transactionRes, info.transactionState)
		return nil
	}

	// Void transaction
	if err := voidPreauth(ctx, client, ref); err != nil {
		return err
	}

	// Verify final state
	finalInfo, err := fetchTransactionInfo(ctx, client, ref)
	if err != nil {
		return err
	}

	if !isSuccessfullyVoided(finalInfo) {
		return fmt.Errorf("unexpected final state res=%s state=%s",
			finalInfo.transactionRes, finalInfo.transactionState)
	}

	log.Infof("Preauth %s successfully voided", ref)
	return markReleased(ctx, dbConn, ref, now)
}

/* ==============================
   State Evaluation Helpers
   ============================== */

func isVoidable(info TransactionInfo) bool {
	return strings.EqualFold(info.transactionRes, types.ResultApproved) &&
		strings.EqualFold(info.transactionState, types.ResultStateUncommitted)
}

func isAlreadyReleased(info TransactionInfo) bool {
	return strings.EqualFold(info.transactionState, types.ResultStateVoided) ||
		strings.EqualFold(info.transactionRes, types.ResultDeclined)
}

func isSuccessfullyVoided(info TransactionInfo) bool {
	return strings.EqualFold(info.transactionRes, types.ResultDeclined) &&
		strings.EqualFold(info.transactionState, types.ResultStateVoided)
}

/* ==============================
   External Operations
   ============================== */

func fetchDuePreauths(
	ctx context.Context,
	dbConn *sql.DB,
	now time.Time,
) ([]types.PreauthRec, error) {

	return db.GetDuePreauths(ctx, dbConn, now, 0)
}

func markReleased(
	ctx context.Context,
	dbConn *sql.DB,
	ref string,
	now time.Time,
) error {

	return db.MarkPreauthReleased(ctx, dbConn, ref, now)
}

func fetchTransactionInfo(
	ctx context.Context,
	client *http.Client,
	ref string,
) (TransactionInfo, error) {

	var tr TransactionResultXML
	var info TransactionInfo

	payload, _ := xml.Marshal(types.TransactionReferenceRequest{
		TransactionReference: ref,
	})

	body, err := postXML(ctx, client, types.LinkTransactionInformation, payload)
	if err != nil {
		return info, err
	}

	if err := tr.ParseTransactionResult(body); err != nil {
		return info, err
	}

	info.FillFromTransactionResult(tr)
	return info, nil
}

func voidPreauth(
	ctx context.Context,
	client *http.Client,
	ref string,
) error {

	var tr TransactionResultXML
	var info TransactionInfo

	payload, _ := xml.Marshal(types.TransactionReferenceRequest{
		TransactionReference: ref,
	})

	body, err := postXML(ctx, client, types.LinkVoidTransaction, payload)
	if err != nil {
		return err
	}

	if err := tr.ParseTransactionResult(body); err != nil {
		return err
	}

	info.FillFromTransactionResult(tr)

	if !strings.EqualFold(info.transactionRes, types.ResultApproved) {
		return fmt.Errorf("void rejected: %s", info.transactionRes)
	}

	return nil
}

/* ==============================
   Low-level HTTP
   ============================== */

func postXML(
	ctx context.Context,
	client *http.Client,
	url string,
	payload []byte,
) ([]byte, error) {

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(payload))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "text/xml")

	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	return io.ReadAll(resp.Body)
}