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TeamAssignment

// TeamAssignment.cdc // Smart contract for randomly assigning NBA Top Shot usernames to NBA teams // Uses Flow's on-chain randomness (revertibleRandom) access(all) contract TeamAssignment { // Event emitted when an assignment is made access(all) event AssignmentMade(username: String, team: String, assignmentIndex: UInt64) // Event emitted when all assignments are complete access(all) event AllAssignmentsComplete(assignments: {UInt64: Assignment}) // Assignment structure access(all) struct Assignment { access(all) let username: String access(all) let team: String access(all) let assignmentIndex: UInt64 access(all) let timestamp: UFix64 init(username: String, team: String, assignmentIndex: UInt64, timestamp: UFix64) { self.username = username self.team = team self.assignmentIndex = assignmentIndex self.timestamp = timestamp } } // Storage for all assignments access(all) var assignments: {UInt64: Assignment} init() { self.assignments = {} } // Main function: Randomly assign all usernames to teams in one transaction // This function uses Flow's revertibleRandom() for on-chain randomness // Combos are passed as arrays of two-team strings like ["Team1, Team2", "Team3, Team4"] access(all) fun assignAllRandomly(usernames: [String], teams: [String], combos: [String]): {UInt64: Assignment} { pre { usernames.length > 0: "Must provide at least one username" (teams.length + combos.length) == usernames.length: "Number of single teams plus combos must equal number of usernames" } var remainingUsernames = usernames var remainingSingleTeams = teams var remainingCombos = combos var result: {UInt64: Assignment} = {} var index: UInt64 = 0 let currentTime = getCurrentBlock().timestamp // Combine single teams and combos into one pool for random assignment var allAssignments: [String] = [] var i = 0 while i < remainingSingleTeams.length { allAssignments.append(remainingSingleTeams[i]) i = i + 1 } i = 0 while i < remainingCombos.length { allAssignments.append(remainingCombos[i]) i = i + 1 } // Loop through and assign each username to a random team or combo while remainingUsernames.length > 0 { // Get random index for username selection let usernameRandomValue = revertibleRandom<UInt64>() let usernameIndex = usernameRandomValue % UInt64(remainingUsernames.length) // Get random index for assignment selection (team or combo) let assignmentRandomValue = revertibleRandom<UInt64>() let assignmentIndex = assignmentRandomValue % UInt64(allAssignments.length) // Get the selected username and assignment (team or combo) let selectedUsername = remainingUsernames[Int(usernameIndex)] let selectedAssignment = allAssignments[Int(assignmentIndex)] // Create assignment let assignment = Assignment( username: selectedUsername, team: selectedAssignment, assignmentIndex: index, timestamp: currentTime ) // Store assignment result[index] = assignment self.assignments[index] = assignment // Emit event for this assignment emit AssignmentMade( username: selectedUsername, team: selectedAssignment, assignmentIndex: index ) // Remove assigned username and assignment from remaining pools remainingUsernames = self.removeElement(arr: remainingUsernames, index: Int(usernameIndex)) allAssignments = self.removeElement(arr: allAssignments, index: Int(assignmentIndex)) index = index + 1 } // Emit completion event emit AllAssignmentsComplete(assignments: result) return result } // Helper function to remove element from array access(all) fun removeElement(arr: [String], index: Int): [String] { var result: [String] = [] var i = 0 while i < arr.length { if i != index { result.append(arr[i]) } i = i + 1 } return result } // Get all assignments access(all) fun getAllAssignments(): {UInt64: Assignment} { return self.assignments } // Get assignment by index access(all) fun getAssignment(index: UInt64): Assignment? { return self.assignments[index] } }