package dojo

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

	"gitea.futuresens.co.uk/futuresens/hardlink/internal/paymentsvc"
	"gitea.futuresens.co.uk/futuresens/hardlink/internal/types"
)

type Config struct {
	BaseURL         string
	APIKey          string
	SoftwareHouseID string
	Version         string
	TerminalID      string
}

type Client struct {
	baseURL         string
	apiKey          string
	version         string
	softwareHouseID string
	terminalID      string
	httpClient      *http.Client
}

func NewClient(cfg Config) (*Client, error) {
	if cfg.BaseURL == "" {
		return nil, fmt.Errorf("dojo base_url is required")
	}
	if cfg.APIKey == "" {
		return nil, fmt.Errorf("dojo api_key is required")
	}
	if cfg.Version == "" {
		cfg.Version = "2026-02-27"
	}
	if cfg.SoftwareHouseID == "" {
		return nil, fmt.Errorf("dojo software_house_id is required")
	}
	if cfg.TerminalID == "" {
		return nil, fmt.Errorf("dojo terminal_id is required")
	}

	return &Client{
		baseURL:         strings.TrimRight(cfg.BaseURL, "/"),
		apiKey:          cfg.APIKey,
		version:         cfg.Version,
		softwareHouseID: cfg.SoftwareHouseID,
		terminalID:      cfg.TerminalID,
		httpClient:      &http.Client{Timeout: 30 * time.Second},
	}, nil
}

func (c *Client) Sale(ctx context.Context, req paymentsvc.SaleRequest) (*paymentsvc.Result, error) {
	if req.Currency == "" {
		req.Currency = "GBP"
	}

	intent, err := c.createPaymentIntent(ctx, req)
	if err != nil {
		return nil, err
	}

	session, err := c.createTerminalSession(ctx, intent.ID)
	if err != nil {
		return nil, err
	}

	session, err = c.waitForTerminalSession(ctx, session.ID)
	if err != nil {
		return nil, err
	}

	switch strings.ToLower(session.Status) {
	case types.ResultCaptured, types.ResultSignatureAccepted:
		intent, err = c.getPaymentIntent(ctx, intent.ID)
		if err != nil {
			return nil, err
		}
		if strings.ToLower(intent.Status) != types.ResultCaptured {
			return nil, fmt.Errorf("Dojo terminal session is %s but payment intent is %s", session.Status, intent.Status)
		}
		return c.mapCapturedResult(req, intent), nil

	case types.ResultCancelled, types.ResultCanceled, types.ResultDeclined, types.ResultExpired, types.ResultSignatureRejected:
		return c.mapTerminalFailure(req, session), nil

	case types.ResultSignatureRequired:
		result := c.baseResult(req, session.PaymentDetails)
		result.Status = "SIGNATURE_VERIFICATION_REQUIRED"
		result.ErrorMessage = "Dojo signature verification is required but is not supported"
		return result, nil

	default:
		return nil, fmt.Errorf("unexpected final Dojo terminal session status %q", session.Status)
	}
}

func (c *Client) createPaymentIntent(ctx context.Context, req paymentsvc.SaleRequest) (*paymentIntentResponse, error) {
	payload := createPaymentIntentRequest{
		Amount: money{
			Value:        req.Amount,
			CurrencyCode: req.Currency,
		},
		Reference:   dojoReference(req),
		CaptureMode: "Auto",
	}

	var response paymentIntentResponse
	if err := c.doJSON(ctx, http.MethodPost, "/payment-intents", payload, false, &response); err != nil {
		return nil, fmt.Errorf("create Dojo payment intent: %w", err)
	}
	if response.ID == "" {
		return nil, fmt.Errorf("create Dojo payment intent: response did not contain id")
	}

	return &response, nil
}

func (c *Client) createTerminalSession(ctx context.Context, paymentIntentID string) (*terminalSessionResponse, error) {
	payload := createTerminalSessionRequest{
		TerminalID: c.terminalID,
		Details: terminalSessionDetails{
			SessionType: "Sale",
			Sale: terminalSessionSale{
				PaymentIntentID: paymentIntentID,
			},
		},
	}

	var response terminalSessionResponse
	if err := c.doJSON(ctx, http.MethodPost, "/terminal-sessions", payload, true, &response); err != nil {
		return nil, fmt.Errorf("create Dojo terminal session: %w", err)
	}
	if response.ID == "" {
		return nil, fmt.Errorf("create Dojo terminal session: response did not contain id")
	}

	return &response, nil
}

func (c *Client) waitForTerminalSession(ctx context.Context, terminalSessionID string) (*terminalSessionResponse, error) {
	ticker := time.NewTicker(time.Second)
	defer ticker.Stop()

	for {
		session, err := c.getTerminalSession(ctx, terminalSessionID)
		if err != nil {
			return nil, err
		}

		switch strings.ToLower(session.Status) {
		case types.ResultInitiateRequested, types.ResultInitiated, types.ResultAuthorized, types.ResultCancelRequested:
			// Still processing. For this integration payment intents use captureMode Auto,
			// so Authorized is expected to continue to Captured.

		case types.ResultCaptured, types.ResultCancelled, types.ResultCanceled, types.ResultDeclined, types.ResultExpired,
			types.ResultSignatureRequired, types.ResultSignatureAccepted,
			types.ResultSignatureRejected:
			return session, nil

		default:
			return nil, fmt.Errorf("unexpected Dojo terminal session status %q", session.Status)
		}

		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-ticker.C:
		}
	}
}

func (c *Client) getTerminalSession(ctx context.Context, terminalSessionID string) (*terminalSessionResponse, error) {
	var response terminalSessionResponse
	path := "/terminal-sessions/" + url.PathEscape(terminalSessionID)
	if err := c.doJSON(ctx, http.MethodGet, path, nil, true, &response); err != nil {
		return nil, fmt.Errorf("get Dojo terminal session: %w", err)
	}
	return &response, nil
}

func (c *Client) getPaymentIntent(ctx context.Context, paymentIntentID string) (*paymentIntentResponse, error) {
	var response paymentIntentResponse
	path := "/payment-intents/" + url.PathEscape(paymentIntentID) + "?returnCanceled=true"
	if err := c.doJSON(ctx, http.MethodGet, path, nil, false, &response); err != nil {
		return nil, fmt.Errorf("get Dojo payment intent: %w", err)
	}
	return &response, nil
}

func (c *Client) mapCapturedResult(req paymentsvc.SaleRequest, intent *paymentIntentResponse) *paymentsvc.Result {
	result := c.baseResult(req, intent.PaymentDetails)
	result.Success = true
	result.Status = "APPROVED"

	if intent.Amount.Value != 0 {
		result.Amount = intent.Amount.Value
	}
	if intent.Amount.CurrencyCode != "" {
		result.Currency = intent.Amount.CurrencyCode
	}
	if result.Message == "" {
		result.Message = "Payment approved"
	}

	return result
}

func (c *Client) mapTerminalFailure(req paymentsvc.SaleRequest, session *terminalSessionResponse) *paymentsvc.Result {
	result := c.baseResult(req, session.PaymentDetails)
	result.Status = strings.ToUpper(session.Status)
	result.ErrorMessage = "Dojo terminal session ended with status " + session.Status
	return result
}

func (c *Client) baseResult(req paymentsvc.SaleRequest, details *paymentDetails) *paymentsvc.Result {
	result := &paymentsvc.Result{
		RequestID:  req.RequestID,
		Operation:  "SALE",
		Amount:     req.Amount,
		Currency:   req.Currency,
		DeviceUsed: c.terminalID,
		DeviceType: "Dojo Terminal",
	}

	if details == nil {
		return result
	}

	result.TransactionID = details.TransactionID
	result.ReferenceNumber = req.RequestID
	result.AuthCode = details.AuthCode
	result.Message = details.Message
	result.CardNumber = details.Card.CardNumber
	result.CardType = details.Card.CardType
	result.ExpiryDate = details.Card.ExpiryDate
	result.LastFourDigits = details.Card.CardNumber

	return result
}

func (c *Client) doJSON(ctx context.Context, method, path string, payload any, terminalRequest bool, target any) error {
	var body io.Reader
	if payload != nil {
		encoded, err := json.Marshal(payload)
		if err != nil {
			return fmt.Errorf("encode request: %w", err)
		}
		body = bytes.NewReader(encoded)
	}

	req, err := http.NewRequestWithContext(ctx, method, c.baseURL+path, body)
	if err != nil {
		return fmt.Errorf("create request: %w", err)
	}

	req.Header.Set("Authorization", "Basic "+c.apiKey)
	req.Header.Set("Version", c.version)
	req.Header.Set("Accept", "application/json")
	if payload != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	if terminalRequest {
		req.Header.Set("software-house-id", c.softwareHouseID)
	}

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

	responseBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return fmt.Errorf("read response: %w", err)
	}

	if resp.StatusCode < http.StatusOK ||
		resp.StatusCode >= http.StatusMultipleChoices {
		return fmt.Errorf("Dojo returned HTTP %d: %s", resp.StatusCode, strings.TrimSpace(string(responseBody)))
	}

	if target == nil || len(responseBody) == 0 {
		return nil
	}
	if err := json.Unmarshal(responseBody, target); err != nil {
		return fmt.Errorf("decode response: %w", err)
	}

	return nil
}

func dojoReference(req paymentsvc.SaleRequest) string {
	reference := req.RequestID
	if reference == "" {
		reference = req.Reference
	}

	runes := []rune(reference)
	if len(runes) > 60 {
		runes = runes[:60]
	}
	return string(runes)
}

func lastFour(cardNumber string) string {
	digits := make([]byte, 0, len(cardNumber))
	for i := 0; i < len(cardNumber); i++ {
		if cardNumber[i] >= '0' && cardNumber[i] <= '9' {
			digits = append(digits, cardNumber[i])
		}
	}
	if len(digits) <= 4 {
		return string(digits)
	}
	return string(digits[len(digits)-4:])
}