package contract

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net/http"
	"strings"
	"time"

	"github.com/jinzhu/gorm"
	"github.com/lib/pq"
	"gitlab.com/pactual1/backend/config"
	"gitlab.com/pactual1/backend/database/device"
	"gitlab.com/pactual1/backend/models"
	"gitlab.com/pactual1/backend/services/blockchain"
	"gitlab.com/pactual1/backend/shared"
)

func GetContracts(status []string, companyName string, companyAddress string,
	companyEmail string, companyPhone string, startTime *time.Time, endTime *time.Time,
	contractName string, deviceIDs []int64, contractIDs []int64, dateCreated *time.Time, limit, offset int) ([]models.Contract, int64, int, error) {

	var contracts []models.Contract
	db := shared.GetDb()
	countDb := db

	// Define custom fields to be selected, varies based on joined tables
	customFields := "distinct contracts.*, array_length(contracts.device_ids, 1) as number_of_devices"

	// Search by Statuses
	if len(status) > 0 {
		db = db.Where("contracts.status IN (?)", status)
		countDb = countDb.Where("contracts.status IN (?)", status)
	}

	// Search by IDs
	if len(contractIDs) > 0 {
		db = db.Where("contracts.id IN (?)", contractIDs)
		countDb = countDb.Where("contracts.id IN (?)", contractIDs)
	}

	// Search by Company Fields
	db = db.Joins("left join companies on companies.id = contracts.buyer_id")
	countDb = countDb.Joins("left join companies on companies.id = contracts.buyer_id")
	customFields += ", companies.name as buyer_name"
	if companyName != "" {
		db = db.Where("companies.name LIKE ?", "%"+companyName+"%")
		countDb = countDb.Where("companies.name LIKE ?", "%"+companyName+"%")
	}
	if companyAddress != "" {
		db = db.Where("companies.address LIKE ?", "%"+companyAddress+"%")
		countDb = countDb.Where("companies.address LIKE ?", "%"+companyAddress+"%")
	}
	if companyEmail != "" {
		db = db.Where("companies.email LIKE ?", "%"+companyEmail+"%")
		countDb = countDb.Where("companies.email LIKE ?", "%"+companyEmail+"%")
	}
	if companyPhone != "" {
		db = db.Where("companies.phone LIKE ?", "%"+companyPhone+"%")
		countDb = countDb.Where("companies.phone LIKE ?", "%"+companyPhone+"%")
	}

	// Search by Contract Name
	if contractName != "" {
		db = db.Where("lower(contracts.name) LIKE ?", "%"+strings.ToLower(contractName)+"%")
		countDb = countDb.Where("lower(contracts.name) LIKE ?", "%"+strings.ToLower(contractName)+"%")
	}

	// Search by Start Time and End Time
	if startTime != nil && !startTime.IsZero() {
		db = db.Where("start_time >= ?", startTime)
		countDb = countDb.Where("start_time >= ?", startTime)
	}

	if endTime != nil && !startTime.IsZero() {
		db = db.Where("end_time <= ?", endTime)
		countDb = countDb.Where("end_time <= ?", endTime)
	}

	if dateCreated != nil && !dateCreated.IsZero() {
		db = db.Where("contracts.created_at = ?", dateCreated)
		countDb = countDb.Where("contracts.created_at = ?", dateCreated)
	}

	// Search by Device IDs
	if len(deviceIDs) > 0 {
		db = db.Where("device_ids && ?", pq.Array(deviceIDs))
		countDb = countDb.Where("device_ids && ?", pq.Array(deviceIDs))
	}

	// Fetch total count of filtered records
	var total int64
	if err := countDb.Model(&models.Contract{}).Count(&total).Error; err != nil {
		log.Printf("GetContracts Error: Database error: %v", err)
		return contracts, total, http.StatusInternalServerError, err
	}

	// Fetch contracts with custom fields
	if err := db.Select(customFields).
		Order("created_at desc").
		Limit(limit).
		Offset(offset).
		Find(&contracts).Error; err != nil {
		if errors.Is(err, gorm.ErrRecordNotFound) {
			log.Printf("GetContracts Error: No contracts found: %v", err)
			return contracts, total, http.StatusNotFound, err
		} else {
			log.Printf("GetContracts Error: Database error: %v", err)
			return contracts, total, http.StatusInternalServerError, err
		}
	}

	return contracts, total, http.StatusOK, nil
}

func UpdateContract(contract models.Contract) (models.Contract, int, error) {
	var devices []models.Device
	var status int
	var err error
	if contract.DeviceIDs != nil {
		devices, status, err = device.GetDevicesByID(contract.DeviceIDs)
		if err != nil {
			return contract, status, err
		}

		status, err = validateContractDevices(contract.ID, devices)
		if err != nil {
			log.Printf("UpdateContract Error: Invalid Device ID: %v", err)
			return contract, status, err
		}
	}

	// get old contract to compare updates
	oldContract, status, err := GetContractByID(contract.ID)
	if err != nil {
		return contract, status, err
	}

	err = shared.GetDb().Transaction(func(tx *gorm.DB) error {
		// Update contract
		if err := tx.Model(contract).Updates(contract).Error; err != nil {
			log.Printf("UpdateContract Error: Could not update contract: %v", err)
			return err
		}

		if devices != nil {
			// Update devices
			if err := tx.Model(models.Device{}).Where("id IN (?)", []int64(contract.DeviceIDs)).Updates(models.Device{CurrentContractID: &contract.ID}).Error; err != nil {
				log.Printf("UpdateContract Error: Could not update devices: %v", err)
				return err
			}
		}

		// return nil will commit the whole transaction
		return nil
	})
	if err != nil {
		log.Printf("UpdateContract Error: Could not update contract: %v", err)
		return contract, http.StatusInternalServerError, err
	}

	contract, status, err = GetContractByID(contract.ID)
	if err != nil {
		return contract, status, err
	}

	// Create contract in blockchain only when it is signed
	if oldContract.Status != contract.Status && contract.Status == models.ContractStatusSigned {
		err = blockchain.NewService(config.AppConfig.Blockchain).CreateContract(context.Background(), shared.CovertUintToByte32(contract.ID))
		if err != nil {
			log.Printf("UpdateContract Error: Could not create contract in blockchain: %v", err)
			return contract, http.StatusInternalServerError, err
		}

		// Register devices in blockchain when contract is signed
		for _, device := range devices {
			err = blockchain.NewService(config.AppConfig.Blockchain).RegisterNewDeviceID(context.Background(), shared.CovertUintToByte32(contract.ID), shared.CovertUintToByte32(device.ID))
			if err != nil {
				log.Printf("UpdateContract Error: Could not register contract device in blockchain: %v", err)
				return contract, http.StatusInternalServerError, err
			}
		}
	}

	return contract, status, err
}

func validateContractDevices(contractID uint, devices []models.Device) (int, error) {

	for _, device := range devices {
		if device.CurrentContractID != nil && *device.CurrentContractID != contractID {
			currentDeviceContract, status, err := GetContractByID(*device.CurrentContractID)
			if err != nil {
				return status, err
			}

			if currentDeviceContract.Status != models.ContractStatusExecuted &&
				currentDeviceContract.Status == models.ContractStatusRevoked {
				return http.StatusBadRequest, fmt.Errorf("device id %d is linked to contract id - %d name %s", device.ID, currentDeviceContract.ID, currentDeviceContract.Name)
			}
		}
	}

	return http.StatusOK, nil
}

func GetContractByID(contractID uint) (models.Contract, int, error) {

	// Fetch the contract creation date based on contractID
	var contract models.Contract
	if err := shared.GetDb().Unscoped().Where("id = ?", contractID).First(&contract).Error; err != nil {
		log.Printf("GetContractByID Error: Could not fetch contract: %v", err)
		return contract, http.StatusInternalServerError, err
	}

	// Fetch the product
	var product models.ProductTemplate
	if err := shared.GetDb().Unscoped().Where("id = ?", contract.ProductID).First(&product).Error; err != nil {
		log.Printf("GetContractByID Error: Could not fetch product: %v", err)
		return contract, http.StatusInternalServerError, err
	}
	contract.ProductName = product.Name

	// Fetch the seller
	var seller models.Company
	if err := shared.GetDb().Unscoped().Where("id = ?", contract.SellerID).First(&seller).Error; err != nil {
		log.Printf("GetContractByID Error: Could not fetch seller: %v", err)
		return contract, http.StatusInternalServerError, err
	}
	contract.SellerName = seller.Name

	// Fetch the buyer
	var buyer models.Company
	if err := shared.GetDb().Unscoped().Where("id = ?", contract.BuyerID).First(&buyer).Error; err != nil {
		log.Printf("GetContractByID Error: Could not fetch buyer: %v", err)
		return contract, http.StatusInternalServerError, err
	}
	contract.BuyerName = buyer.Name

	return contract, http.StatusOK, nil
}