;; BitTrust Core Lending Contract
;; A reputation-based micro-lending platform on Stacks
;; Constants
(define-constant contract-owner tx-sender)
(define-constant err-owner-only (err u100))
(define-constant err-not-found (err u101))
(define-constant err-unauthorized (err u102))
(define-constant err-insufficient-collateral (err u103))
(define-constant err-loan-active (err u104))
(define-constant err-loan-not-active (err u105))
(define-constant err-invalid-amount (err u106))
(define-constant err-already-exists (err u107))
(define-constant err-insufficient-balance (err u108))
;; Data Variables
(define-data-var loan-nonce uint u0)
;; Data Maps
(define-map loans
{ loan-id: uint }
{
borrower: principal,
lender: principal,
amount: uint,
collateral: uint,
interest-rate: uint,
duration: uint,
start-block: uint,
due-block: uint,
repaid-amount: uint,
status: (string-ascii 20),
collateral-ratio: uint
}
)
(define-map user-stats
{ user: principal }
{
total-borrowed: uint,
total-lent: uint,
active-loans-as-borrower: uint,
active-loans-as-lender: uint,
total-repaid: uint,
defaults: uint
}
)
(define-map collateral-vault
{ loan-id: uint }
{ amount: uint }
)
;; Read-only functions
(define-read-only (get-loan (loan-id uint))
(map-get? loans { loan-id: loan-id })
)
(define-read-only (get-user-stats (user principal))
(default-to
{ total-borrowed: u0, total-lent: u0, active-loans-as-borrower: u0,
active-loans-as-lender: u0, total-repaid: u0, defaults: u0 }
(map-get? user-stats { user: user })
)
)
(define-read-only (calculate-repayment-amount (loan-id uint))
(let
(
(loan (unwrap! (get-loan loan-id) err-not-found))
(principal-amount (get amount loan))
(interest-rate (get interest-rate loan))
)
(ok (+ principal-amount (/ (* principal-amount interest-rate) u10000)))
)
)
(define-read-only (is-loan-overdue (loan-id uint))
(let
(
(loan (unwrap! (get-loan loan-id) err-not-found))
)
(ok (> stacks-block-height (get due-block loan)))
)
)
;; Public functions
;; Create a direct peer-to-peer loan
(define-public (create-loan (borrower principal) (amount uint) (collateral-amount uint)
(interest-rate uint) (duration uint) (min-collateral-ratio uint))
(let
(
(loan-id (var-get loan-nonce))
(collateral-ratio (if (> collateral-amount u0)
(/ (* collateral-amount u100) amount)
u0))
)
(asserts! (> amount u0) err-invalid-amount)
(asserts! (not (is-eq borrower tx-sender)) err-invalid-amount)
(asserts! (<= interest-rate u10000) err-invalid-amount) ;; Max 100%
(asserts! (> duration u0) err-invalid-amount)
(asserts! (>= collateral-ratio min-collateral-ratio) err-insufficient-collateral)
;; Transfer loan from lender to borrower
(try! (stx-transfer? amount tx-sender borrower))
;; Transfer collateral from borrower to lender (held as collateral)
(if (> collateral-amount u0)
(try! (stx-transfer? collateral-amount borrower tx-sender))
true
)
;; Store collateral info
(map-set collateral-vault { loan-id: loan-id } { amount: collateral-amount })
;; Create loan record
(map-set loans
{ loan-id: loan-id }
{
borrower: borrower,
lender: tx-sender,
amount: amount,
collateral: collateral-amount,
interest-rate: interest-rate,
duration: duration,
start-block: stacks-block-height,
due-block: (+ stacks-block-height duration),
repaid-amount: u0,
status: "active",
collateral-ratio: collateral-ratio
}
)
;; Update user stats
(update-user-stats-borrow borrower amount)
(update-user-stats-lend tx-sender amount)
(var-set loan-nonce (+ loan-id u1))
(ok loan-id)
)
)
;; Repay loan
(define-public (repay-loan (loan-id uint) (amount uint))
(let
(
(loan (unwrap! (get-loan loan-id) err-not-found))
(borrower (get borrower loan))
(lender (get lender loan))
(total-repayment (unwrap! (calculate-repayment-amount loan-id) err-not-found))
(new-repaid (+ (get repaid-amount loan) amount))
(collateral-amt (get collateral loan))
)
(asserts! (is-eq tx-sender borrower) err-unauthorized)
(asserts! (is-eq (get status loan) "active") err-loan-not-active)
(asserts! (> amount u0) err-invalid-amount)
;; Transfer repayment to lender
(try! (stx-transfer? amount tx-sender lender))
;; Check if fully repaid
(if (>= new-repaid total-repayment)
(begin
;; Loan fully repaid - return collateral
(map-set loans { loan-id: loan-id } (merge loan {
repaid-amount: new-repaid,
status: "repaid"
}))
;; Return collateral from lender to borrower
(if (> collateral-amt u0)
(try! (stx-transfer? collateral-amt lender borrower))
true
)
;; Update stats
(update-user-stats-repay borrower (get amount loan))
(update-user-stats-lend-complete lender)
)
;; Partial repayment
(map-set loans { loan-id: loan-id } (merge loan { repaid-amount: new-repaid }))
)
(ok true)
)
)
;; Liquidate defaulted loan
(define-public (liquidate-loan (loan-id uint))
(let
(
(loan (unwrap! (get-loan loan-id) err-not-found))
(lender (get lender loan))
)
(asserts! (is-eq tx-sender lender) err-unauthorized)
(asserts! (is-eq (get status loan) "active") err-loan-not-active)
(asserts! (unwrap! (is-loan-overdue loan-id) err-not-found) err-loan-active)
;; Update loan status (collateral already with lender)
(map-set loans { loan-id: loan-id } (merge loan { status: "liquidated" }))
;; Update borrower stats (add default)
(let
(
(borrower (get borrower loan))
(stats (get-user-stats borrower))
)
(map-set user-stats
{ user: borrower }
(merge stats {
defaults: (+ (get defaults stats) u1),
active-loans-as-borrower: (- (get active-loans-as-borrower stats) u1)
})
)
)
(ok true)
)
)
;; Private functions
(define-private (update-user-stats-borrow (user principal) (amount uint))
(let
(
(stats (get-user-stats user))
)
(map-set user-stats
{ user: user }
{
total-borrowed: (+ (get total-borrowed stats) amount),
total-lent: (get total-lent stats),
active-loans-as-borrower: (+ (get active-loans-as-borrower stats) u1),
active-loans-as-lender: (get active-loans-as-lender stats),
total-repaid: (get total-repaid stats),
defaults: (get defaults stats)
}
)
)
)
(define-private (update-user-stats-lend (user principal) (amount uint))
(let
(
(stats (get-user-stats user))
)
(map-set user-stats
{ user: user }
{
total-borrowed: (get total-borrowed stats),
total-lent: (+ (get total-lent stats) amount),
active-loans-as-borrower: (get active-loans-as-borrower stats),
active-loans-as-lender: (+ (get active-loans-as-lender stats) u1),
total-repaid: (get total-repaid stats),
defaults: (get defaults stats)
}
)
)
)
(define-private (update-user-stats-repay (user principal) (amount uint))
(let
(
(stats (get-user-stats user))
)
(map-set user-stats
{ user: user }
(merge stats {
total-repaid: (+ (get total-repaid stats) amount),
active-loans-as-borrower: (- (get active-loans-as-borrower stats) u1)
})
)
)
)
(define-private (update-user-stats-lend-complete (user principal))
(let
(
(stats (get-user-stats user))
)
(map-set user-stats
{ user: user }
(merge stats {
active-loans-as-lender: (- (get active-loans-as-lender stats) u1)
})
)
)
)