feat: added basic backend features to it

  - Set up API framework (Gin Gonic)
  - Set up ORM/DB library (GORM)
  - Design database schema (Users, Accounts, Transactions, Loans, Goals)
  - Set up database connection and migrations

1 files changed, 97 insertions, 0 deletions

diff --git a/backend/internal/models/models.go b/backend/internal/models/models.go
new file mode 100644
index 0000000..c984012
--- /dev/null
+++ b/backend/internal/models/models.go
@@ -0,0 +1,97 @@
+package models
+
+import (
+	"time"
+
+	"golang.org/x/crypto/bcrypt"
+	"gorm.io/gorm"
+)
+
+// User represents a user in the system
+// We'll store a hashed password, not the plaintext one.
+type User struct {
+	gorm.Model          // Includes ID, CreatedAt, UpdatedAt, DeletedAt
+	Name         string `gorm:"not null"`
+	Email        string `gorm:"uniqueIndex;not null"` // Unique email
+	PasswordHash string `gorm:"not null"`             // Store hashed password
+}
+
+// SetPassword hashes the given password and sets it on the user model.
+func (u *User) SetPassword(password string) error {
+	hashedPassword, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return err
+	}
+	u.PasswordHash = string(hashedPassword)
+	return nil
+}
+
+// CheckPassword compares a given password with the user's hashed password.
+// Returns nil if the password is correct, otherwise returns an error.
+func (u *User) CheckPassword(password string) error {
+	return bcrypt.CompareHashAndPassword([]byte(u.PasswordHash), []byte(password))
+}
+
+// Account represents a financial account (e.g., bank account, credit card, cash)
+// It belongs to a User.
+type Account struct {
+	gorm.Model
+	UserID uint   `gorm:"not null;index"` // Foreign key to User
+	User   User   // Belongs To relationship
+	Name   string `gorm:"not null"`
+	Type   string `gorm:"not null;index"` // e.g., "Bank", "Credit Card", "Cash", "Loan", "Income Source"
+	// Balance is stored in the smallest currency unit (e.g., cents)
+	// to avoid floating point issues.
+	Balance int64 `gorm:"not null;default:0"`
+}
+
+// Transaction represents an income or expense event.
+// It belongs to a User and is usually associated with an Account.
+type Transaction struct {
+	gorm.Model
+	UserID      uint     `gorm:"not null;index"` // Foreign key to User
+	User        User     // Belongs To relationship
+	AccountID   *uint    `gorm:"index"` // Foreign key to Account (nullable, e.g., for cash transactions not tied to a bank)
+	Account     *Account // Belongs To relationship (pointer for nullable FK)
+	Description string   `gorm:"not null"`
+	// Amount stored in the smallest currency unit (e.g., cents)
+	Amount   int64     `gorm:"not null"`
+	Type     string    `gorm:"not null;index"` // "Income" or "Expense"
+	Date     time.Time `gorm:"not null;index"` // Date of the transaction
+	Category string    `gorm:"index"`          // e.g., "Salary", "Groceries", "Utilities"
+}
+
+// Loan represents a loan taken by the user.
+// It belongs to a User and may be linked to an Account representing the loan source/payments.
+type Loan struct {
+	gorm.Model
+	UserID         uint     `gorm:"not null;index"` // Foreign key to User
+	User           User     // Belongs To relationship
+	AccountID      *uint    `gorm:"index"` // Optional FK to the related Account (e.g., where payments are made from/to)
+	Account        *Account // Belongs To relationship
+	Name           string   `gorm:"not null"` // e.g., "Car Loan", "Student Loan"
+	OriginalAmount int64    `gorm:"not null"` // In smallest currency unit
+	CurrentBalance int64    `gorm:"not null"` // In smallest currency unit
+	InterestRate   float64  // Annual interest rate (e.g., 0.05 for 5%)
+	StartDate      time.Time
+	EndDate        time.Time // Expected payoff date
+	// Add fields for payment frequency, next due date etc. if needed later
+}
+
+// Goal represents a financial goal the user is working towards.
+// It belongs to a User.
+type Goal struct {
+	gorm.Model
+	UserID        uint      `gorm:"not null;index"` // Foreign key to User
+	User          User      // Belongs To relationship
+	Name          string    `gorm:"not null"`           // e.g., "Save for Down Payment", "Pay Off Credit Card"
+	TargetAmount  int64     `gorm:"not null"`           // In smallest currency unit
+	CurrentAmount int64     `gorm:"not null;default:0"` // In smallest currency unit
+	TargetDate    time.Time // Optional target date for the goal
+	Status        string    `gorm:"not null;default:'Active';index"` // e.g., "Active", "Achieved", "Cancelled"
+	// Link to specific accounts or loans if needed (e.g., goal to pay off a specific loan)
+	// RelatedAccountID *uint
+	// RelatedLoanID *uint
+}
+
+// Add other models below (Goal)