Mermaid Modelling Syntax
===
## 1. FLow Chart
* Euclide GCD

graph LR
    st((Start)) --> iput[/"Read a, b"/]
    iput --> op1["int tmp"]
    op1 --> cond1{"b != 0"}
    cond1 --> |True| op2["tmp <- b <br> b <- a % b <br> a <- tmp"]
    op2 --> cond1
    cond1 --> |False| op3["result <- a"]
    op3 --> oput[/"print result"/];
    oput --> e
    e((End))

* Quadratic Equation

  graph LR;
    st((Start)) --> iput[/"Read a, b, c"/]
    e((end))
    iput --> cond1{a = 0}
    cond1 --> |True| cond2{b = 0}
    cond1 --> |False| op[Del = b*b + 4*a*c] 

    cond2 --> |True| cond3{c = 0}
    cond2 --> |False| oput1[/"Phương trình có nghiệm: <br> x = -c/b"/]

    cond3 --> |True| oput2[/"Phương trình có vô số nghiệm"/]
    cond3 --> |False| oput3[/"Phương trình vô nghiệm"/]

    op --> cond5{Del > 0}
    cond5 --> |True| oput4[/"Phương trình có 2 nghiệm phân biệt: <br> x1 = (b*b - sqrt(Del)) / (2*a) <br> x2 = (b*b + sqrt(Del)) / (2*a)"/]
    cond5 --> |False| cond6{Del = 0}

    cond6 --> |True| oput5[/"Phương trình có nghiệm kép:<br> x = -b/(2*a)"/]
    cond6 --> |False| oput6[/"Phương trình vô nghiệm"/]

    oput1 --> e
    oput2 --> e
    oput3 --> e
    oput4 --> e
    oput5 --> e
    oput6 --> e

## 2. Class Diagram

classDiagram
  Customer <|-- PremiumCustomer
  Customer <|-- RegularCustomer
  Customer : custName: String
  Customer : custID: String
  Customer : custPhNum: int
  Customer: purchaseItem()
  Customer: requestBill()
  Customer: enterCustDetail()

  PremiumCustomer : premiumDiscount: int
  PremiumCustomer: enterCustDetail()

  RegularCustomer : regularDiscount: int
  RegularCustomer: enterCustDetail()

  Customer "1" *-- "1"Address: Has
  Address : street: String 
  Address : city: String 
  Address : state: String 
  Address : zipcode: int 
  Address: enterStreet()
  Address: enterCity()
  Address: enterState()
  Address: enterZipcode()

  Customer"1" -- "*"Product: Is Sold To
  Product : productID: int
  Product : productName: String
  Product : productPrice: Float
  Product: getPrice()
  Product: setPrice()
  Product -- PurchaseDetail

  Customer -- PurchaseDetail
  PurchaseDetail : custID: int
  PurchaseDetail : quaranty: int
  PurchaseDetail : purchaseDate: Date
  PurchaseDetail : productID: int
  PurchaseDetail: calculateTotalAmt()
  PurchaseDetail: generatePurchaseList()

  Bill --o Customer: Belongs to
  Bill : payableAmt
  Bill: calculatePayableAmt()
  Bill: generateBill()

  Bill ..>Discount
  Discount : discountType
  Discount : discountValue
  Discount: SelectDiscount()

  Discount..>PurchaseDetail
  Bill..>PurchaseDetail

  Bill..|> PaymentCounter: Accepts
  
  class PaymentCounter{
    << interface >>
    calculatePayableAmt()
    generateBill()	
 }
		

## 3. Sequence Diagram

sequenceDiagram
    participant Customer
    participant Search Page
    participant Search Results Page
    participant Catalog
    participant Search Results
    
    activate Customer
    Customer ->> Search Page: 1: onSearch(author)
    activate Search Page
        Search Page ->> Search Page: 1.1: validateSearchCriteria()
        alt author entered

            Search Page ->> Catalog: 1.2: searchByAuthor(author)
            activate Catalog
                Catalog ->> Search Results: 1.2.1: create()
                activate Search Results

                    Search Results ->> Search Results Page: 1.2.1.1: display()
                    activate Search Results Page
                    deactivate Search Results Page
                deactivate Search Results

        else author not entered
            deactivate Catalog
            Search Page ->> Search Page: 1.3: displayErrorMessage()
        end
    deactivate Search Page
    deactivate Customer

## 4. State Chart Diagram
### ATM State Machine Diagram

stateDiagram
 s1: PrintReceipt
 s2: DispenseMoney
 s3: AccountActions
 s4: Idle
 
 s2 --> s1
 s3 --> s2
 s3 --> s1
 [*] --> s4
 s1 --> [*]
 s2 --> [*]
 s4 --> VerifyAccount
 state VerifyAccount{
  state "VerifyCard" as s5
     s5:cardSubmitted /
     s5:readCard /
     s5:returnCard /
  s6: CardValid
  s7: PinCorrect
  state "VerifyPin" as s8
     s8 : pinSubmitted /
     s8 : checkPin /
     s8 : returnCard /
  s9: PinInCorrect
  
             
  s5 --> CardValid
  CardValid --> s6: cardValid
  s6 --> s8
  s8 --> PinCorrect
  PinCorrect --> s7: [PinValid]
  PinCorrect --> s9:[else]
  s9 --> s8: [tries < maxtries] / tries++ 
}