package square

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"time"
)

// ErrCheckoutPending is returned by GetCheckout when a terminal checkout has
// not yet completed. Handlers use errors.Is(err, ErrCheckoutPending) rather
// than string comparison, so behaviour is identical across the mock and the
// real HTTP client.
var ErrCheckoutPending = errors.New("checkout pending")

// ---------------------------------------------------------------------------
// Square REST API constants.
// ---------------------------------------------------------------------------

const (
	squareSandboxURL    = "https://connect.squareupsandbox.com"
	squareProductionURL = "https://connect.squareup.com"
	squareAPIVersion    = "2026-05-20"
	defaultHTTPTimeout  = 30 * time.Second
)

// ---------------------------------------------------------------------------
// HTTP client — shared by ProdClient (!dev) and devProdClient (dev).
// ---------------------------------------------------------------------------

type httpClient struct {
	baseURL    string
	token      string
	locationID string
	http       *http.Client
}

func newHTTPClient() *httpClient {
	env := os.Getenv("SQUARE_ENVIRONMENT")
	baseURL := squareSandboxURL
	if env == "production" {
		baseURL = squareProductionURL
	}
	return &httpClient{
		baseURL:    baseURL,
		token:      os.Getenv("SQUARE_ACCESS_TOKEN"),
		locationID: os.Getenv("SQUARE_LOCATION_ID"),
		http:       &http.Client{Timeout: defaultHTTPTimeout},
	}
}

func (c *httpClient) doJSON(ctx context.Context, method, path string, body, target any) error {
	if c.token == "" {
		return fmt.Errorf("square: SQUARE_ACCESS_TOKEN is not set")
	}
	var reqBody []byte
	if body != nil {
		var err error
		reqBody, err = json.Marshal(body)
		if err != nil {
			return fmt.Errorf("square: marshal request: %w", err)
		}
	}
	url := c.baseURL + path
	req, err := http.NewRequestWithContext(ctx, method, url, bytes.NewReader(reqBody))
	if err != nil {
		return fmt.Errorf("square: create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Square-Version", squareAPIVersion)
	req.Header.Set("Authorization", "Bearer "+c.token)

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("square: %s %s: %w", method, path, err)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("square: read response: %w", err)
	}
	if resp.StatusCode >= 300 {
		var errResp struct{ Errors []SquareError `json:"errors"` }
		if json.Unmarshal(respBody, &errResp) == nil && len(errResp.Errors) > 0 {
			se := errResp.Errors[0]
			return fmt.Errorf("square: %s %s: [%s/%s] %s (field: %s)", method, path, se.Category, se.Code, se.Detail, se.Field)
		}
		return fmt.Errorf("square: %s %s: HTTP %d: %s", method, path, resp.StatusCode, string(respBody))
	}
	if target != nil && len(respBody) > 0 {
		if err := json.Unmarshal(respBody, target); err != nil {
			return fmt.Errorf("square: unmarshal response: %w", err)
		}
	}
	return nil
}

// ---------------------------------------------------------------------------
// Square JSON types — exact wire-format match with Square's REST API.
// ---------------------------------------------------------------------------

type sqMoney struct {
	Amount   int64  `json:"amount"`
	Currency string `json:"currency"`
}

// --- Payment types ---

type sqCreatePaymentRequest struct {
	SourceID          string   `json:"source_id"`
	IdempotencyKey    string   `json:"idempotency_key"`
	AmountMoney       sqMoney  `json:"amount_money"`
	Autocomplete      *bool    `json:"autocomplete,omitempty"`
	LocationID        string   `json:"location_id,omitempty"`
	ReferenceID       string   `json:"reference_id,omitempty"`
	CustomerID        string   `json:"customer_id,omitempty"`
	Note              string   `json:"note,omitempty"`
	TipMoney          *sqMoney `json:"tip_money,omitempty"`
	VerificationToken string   `json:"verification_token,omitempty"`
	BuyerEmailAddress string   `json:"buyer_email_address,omitempty"`
}

type sqCreatePaymentResponse struct {
	Payment sqPayment `json:"payment"`
}

type sqPayment struct {
	ID            string         `json:"id"`
	Status        string         `json:"status"`
	TotalMoney    sqMoney        `json:"total_money"`
	TipMoney      *sqMoney       `json:"tip_money,omitempty"`
	SourceType    string         `json:"source_type"`
	CardDetails   *sqCardDetails `json:"card_details,omitempty"`
	LocationID    string         `json:"location_id"`
	OrderID       string         `json:"order_id,omitempty"`
	ReferenceID   string         `json:"reference_id,omitempty"`
	CustomerID    string         `json:"customer_id,omitempty"`
	BuyerEmail    string         `json:"buyer_email_address,omitempty"`
	ReceiptNumber string         `json:"receipt_number,omitempty"`
	ReceiptURL    string         `json:"receipt_url,omitempty"`
	ProcessingFee []sqFee        `json:"processing_fee,omitempty"`
	CreatedAt     string         `json:"created_at"`
	UpdatedAt     string         `json:"updated_at,omitempty"`
}

type sqCardDetails struct {
	Card        sqCard `json:"card"`
	EntryMethod string `json:"entry_method"`
	CVVStatus   string `json:"cvv_status,omitempty"`
	AVSStatus   string `json:"avs_status,omitempty"`
}

type sqCard struct {
	ID             string `json:"id"`
	CardBrand      string `json:"card_brand"`
	Last4          string `json:"last_4"`
	ExpMonth       int    `json:"exp_month"`
	ExpYear        int    `json:"exp_year"`
	CardholderName string `json:"cardholder_name,omitempty"`
	Fingerprint    string `json:"fingerprint"`
	CustomerID     string `json:"customer_id,omitempty"`
	Enabled        bool   `json:"enabled"`
	Version        int64  `json:"version"`
	CreatedAt      string `json:"created_at"`
}

type sqFee struct {
	Amount int64  `json:"amount"`
	Type   string `json:"type"`
}

// --- Terminal Checkout types ---

type sqTerminalCheckoutRequest struct {
	IdempotencyKey string                    `json:"idempotency_key"`
	Checkout       sqTerminalCheckoutPayload `json:"checkout"`
}

type sqTerminalCheckoutPayload struct {
	AmountMoney  sqMoney                 `json:"amount_money"`
	ReferenceID  string                  `json:"reference_id,omitempty"`
	Note         string                  `json:"note,omitempty"`
	CustomerID   string                  `json:"customer_id,omitempty"`
	DeviceOptions *sqDeviceOptions       `json:"device_options,omitempty"`
}

type sqDeviceOptions struct {
	DeviceID string `json:"device_id"`
}

type sqTerminalCheckoutResponse struct {
	Checkout sqTerminalCheckout `json:"checkout"`
}

type sqTerminalCheckout struct {
	ID          string   `json:"id"`
	Status      string   `json:"status"`
	AmountMoney sqMoney  `json:"amount_money"`
	DeviceID    string   `json:"device_id,omitempty"`
	ReferenceID string   `json:"reference_id,omitempty"`
	Note        string   `json:"note,omitempty"`
	PaymentIDs  []string `json:"payment_ids,omitempty"`
	Deadline    string   `json:"deadline_duration,omitempty"`
	CreatedAt   string   `json:"created_at"`
	UpdatedAt   string   `json:"updated_at"`
}

type sqGetPaymentResponse struct {
	Payment sqPayment `json:"payment"`
}

// --- Refund types ---

type sqRefundPaymentRequest struct {
	PaymentID      string  `json:"payment_id"`
	IdempotencyKey string  `json:"idempotency_key"`
	AmountMoney    sqMoney `json:"amount_money"`
	Reason         string  `json:"reason,omitempty"`
}

type sqRefundPaymentResponse struct {
	Refund sqRefund `json:"refund"`
}

type sqRefund struct {
	ID          string  `json:"id"`
	Status      string  `json:"status"`
	AmountMoney sqMoney `json:"amount_money"`
	PaymentID   string  `json:"payment_id"`
	LocationID  string  `json:"location_id"`
	Reason      string  `json:"reason,omitempty"`
	CreatedAt   string  `json:"created_at"`
}

// --- Card types ---

type sqCreateCardRequest struct {
	IdempotencyKey string        `json:"idempotency_key"`
	SourceID       string        `json:"source_id"`
	Card           sqCardPayload `json:"card"`
}

type sqCardPayload struct {
	ExpMonth       *int   `json:"exp_month,omitempty"`
	ExpYear        *int   `json:"exp_year,omitempty"`
	CardholderName string `json:"cardholder_name,omitempty"`
	CustomerID     string `json:"customer_id,omitempty"`
}

type sqCreateCardResponse struct {
	Card sqCard `json:"card"`
}

type sqListCardsResponse struct {
	Cards []sqCard `json:"cards"`
}

type sqDisableCardResponse struct {
	Card sqCard `json:"card"`
}

// ---------------------------------------------------------------------------
// Package-level HTTP functions — shared by ProdClient and devProdClient.
// Each builds a fresh httpClient from env vars and makes the Square API call.
// ---------------------------------------------------------------------------

func createPaymentHTTP(ctx context.Context, req CreatePaymentReq) (*PaymentResult, error) {
	hc := newHTTPClient()
	body := sqCreatePaymentRequest{
		SourceID:          req.SourceID,
		IdempotencyKey:    req.IdempotencyKey,
		AmountMoney:       sqMoney{Amount: req.Amount, Currency: req.Currency},
		Autocomplete:      req.Autocomplete,
		LocationID:        firstNonEmpty(req.LocationID, hc.locationID),
		ReferenceID:       req.ReferenceID,
		CustomerID:        req.CustomerID,
		Note:              req.Note,
		VerificationToken: req.VerificationToken,
		BuyerEmailAddress: req.BuyerEmail,
	}
	if req.TipMoney != nil {
		body.TipMoney = &sqMoney{Amount: *req.TipMoney, Currency: req.Currency}
	}
	var resp sqCreatePaymentResponse
	if err := hc.doJSON(ctx, http.MethodPost, "/v2/payments", body, &resp); err != nil {
		return nil, err
	}
	return paymentFromSquare(&resp.Payment), nil
}

func createCheckoutHTTP(ctx context.Context, req CreateCheckoutReq) (*CheckoutResult, error) {
	return createCheckoutHTTPWithClient(ctx, req, newHTTPClient())
}

func createCheckoutHTTPWithClient(ctx context.Context, req CreateCheckoutReq, hc *httpClient) (*CheckoutResult, error) {
	body := sqTerminalCheckoutRequest{
		IdempotencyKey: req.IdempotencyKey,
		Checkout: sqTerminalCheckoutPayload{
			AmountMoney: sqMoney{Amount: req.Amount, Currency: req.Currency},
			ReferenceID: req.ReferenceID,
			Note:        req.Note,
			CustomerID:  req.CustomerID,
		},
	}
	if req.DeviceID != "" {
		body.Checkout.DeviceOptions = &sqDeviceOptions{DeviceID: req.DeviceID}
	}
	var resp sqTerminalCheckoutResponse
	if err := hc.doJSON(ctx, http.MethodPost, "/v2/terminals/checkouts", body, &resp); err != nil {
		return nil, err
	}
	return checkoutFromSquare(&resp.Checkout), nil
}

func getCheckoutHTTP(ctx context.Context, checkoutID string) (*PaymentResult, error) {
	hc := newHTTPClient()
	var tcResp sqTerminalCheckoutResponse
	if err := hc.doJSON(ctx, http.MethodGet, "/v2/terminals/checkouts/"+checkoutID, nil, &tcResp); err != nil {
		return nil, err
	}
	tc := tcResp.Checkout
	if tc.Status != "COMPLETED" {
		if tc.Status == "PENDING" || tc.Status == "IN_PROGRESS" {
			return nil, ErrCheckoutPending
		}
		return nil, fmt.Errorf("square: checkout %s is %s (not COMPLETED)", checkoutID, tc.Status)
	}
	if len(tc.PaymentIDs) == 0 {
		return nil, fmt.Errorf("square: checkout %s has no payment IDs", checkoutID)
	}
	var payResp sqGetPaymentResponse
	if err := hc.doJSON(ctx, http.MethodGet, "/v2/payments/"+tc.PaymentIDs[0], nil, &payResp); err != nil {
		return nil, err
	}
	return paymentFromSquare(&payResp.Payment), nil
}

func refundPaymentHTTP(ctx context.Context, req RefundPaymentReq) (*RefundResult, error) {
	hc := newHTTPClient()
	body := sqRefundPaymentRequest{
		PaymentID:      req.PaymentID,
		IdempotencyKey: req.IdempotencyKey,
		AmountMoney:    sqMoney{Amount: req.Amount, Currency: "GBP"},
		Reason:         req.Reason,
	}
	var resp sqRefundPaymentResponse
	if err := hc.doJSON(ctx, http.MethodPost, "/v2/refunds", body, &resp); err != nil {
		return nil, err
	}
	return refundFromSquare(&resp.Refund), nil
}

func createCardOnFileHTTP(ctx context.Context, userID, cardToken string) (*CardOnFile, error) {
	hc := newHTTPClient()

	// Deterministic idempotency key derived from user + card (not time-based)
	// so that retries with the same details don't create duplicate cards.
	// SHA-256 hash prevents recovering the card token from the key itself.
	ikHash := sha256.Sum256([]byte(userID + "|" + cardToken))
	body := sqCreateCardRequest{
		IdempotencyKey: fmt.Sprintf("create-card-%x", ikHash),
		SourceID:       cardToken,
		Card: sqCardPayload{
			CustomerID: userID,
		},
	}
	var resp sqCreateCardResponse
	if err := hc.doJSON(ctx, http.MethodPost, "/v2/cards", body, &resp); err != nil {
		return nil, err
	}
	return cardFromSquare(&resp.Card, userID), nil
}

func getCardsOnFileHTTP(ctx context.Context, userID string) ([]CardOnFile, error) {
	hc := newHTTPClient()
	var resp sqListCardsResponse
	if err := hc.doJSON(ctx, http.MethodGet, "/v2/cards?customer_id="+url.QueryEscape(userID), nil, &resp); err != nil {
		return nil, err
	}
	cards := make([]CardOnFile, 0, len(resp.Cards))
	for i := range resp.Cards {
		cards = append(cards, *cardFromSquare(&resp.Cards[i], userID))
	}
	return cards, nil
}

func deleteCardOnFileHTTP(ctx context.Context, cardID string) error {
	hc := newHTTPClient()
	var resp sqDisableCardResponse
	if err := hc.doJSON(ctx, http.MethodPost, "/v2/cards/"+cardID+"/disable", nil, &resp); err != nil {
		return err
	}
	return nil
}

// ---------------------------------------------------------------------------
// Conversion helpers — Square JSON → domain types.
// ---------------------------------------------------------------------------

func paymentFromSquare(sq *sqPayment) *PaymentResult {
	r := &PaymentResult{
		ID:            sq.ID,
		Status:        sq.Status,
		Amount:        sq.TotalMoney.Amount,
		ReceiptURL:    sq.ReceiptURL,
		ReceiptNumber: sq.ReceiptNumber,
		SquarePayID:   sq.ID,
		BuyerEmail:    sq.BuyerEmail,
		CustomerID:    sq.CustomerID,
		LocationID:    sq.LocationID,
		CreatedAt:     sq.CreatedAt,
		UpdatedAt:     sq.UpdatedAt,
		OrderID:       sq.OrderID,
		ReferenceID:   sq.ReferenceID,
	}
	if sq.TipMoney != nil {
		r.TipAmount = sq.TipMoney.Amount
	}
	for _, f := range sq.ProcessingFee {
		r.Fees += f.Amount
	}
	if sq.CardDetails != nil {
		cd := sq.CardDetails
		r.EntryMethod = cd.EntryMethod
		r.CVVStatus = cd.CVVStatus
		r.AVSStatus = cd.AVSStatus
		if cd.Card.ID != "" {
			r.CardBrand = cd.Card.CardBrand
			r.CardLast4 = cd.Card.Last4
			r.CardFingerprint = cd.Card.Fingerprint
			r.ExpMonth = cd.Card.ExpMonth
			r.ExpYear = cd.Card.ExpYear
		} else {
			// Card details present but no card ID — still surface the brand/last4.
			r.CardBrand = cd.Card.CardBrand
			r.CardLast4 = cd.Card.Last4
		}
	}
	return r
}

func checkoutFromSquare(sq *sqTerminalCheckout) *CheckoutResult {
	return &CheckoutResult{
		ID:          sq.ID,
		Status:      sq.Status,
		AmountMoney: sq.AmountMoney.Amount,
		Currency:    sq.AmountMoney.Currency,
		DeviceID:    sq.DeviceID,
		ReferenceID: sq.ReferenceID,
		Note:        sq.Note,
		PaymentIDs:  sq.PaymentIDs,
		Deadline:    sq.Deadline,
		CreatedAt:   sq.CreatedAt,
		UpdatedAt:   sq.UpdatedAt,
	}
}

func refundFromSquare(sq *sqRefund) *RefundResult {
	return &RefundResult{
		ID:         sq.ID,
		Status:     sq.Status,
		Amount:     sq.AmountMoney.Amount,
		PaymentID:  sq.PaymentID,
		LocationID: sq.LocationID,
		Reason:     sq.Reason,
		CreatedAt:  sq.CreatedAt,
	}
}

func cardFromSquare(sq *sqCard, userID string) *CardOnFile {
	customerID := sq.CustomerID
	if customerID == "" {
		customerID = userID
	}
	return &CardOnFile{
		ID:             sq.ID,
		CardID:         sq.ID,
		Brand:          sq.CardBrand,
		Last4:          sq.Last4,
		ExpMonth:       sq.ExpMonth,
		ExpYear:        sq.ExpYear,
		Fingerprint:    sq.Fingerprint,
		CardholderName: sq.CardholderName,
		CustomerID:     customerID,
		Enabled:        sq.Enabled,
		Version:        sq.Version,
		CreatedAt:      sq.CreatedAt,
	}
}

func firstNonEmpty(vals ...string) string {
	for _, v := range vals {
		if v != "" {
			return v
		}
	}
	return ""
}