-- Atomic ticket purchase script
-- KEYS[1]: event tickets key (e.g., "event:1:tickets")
-- KEYS[2]: event metadata key (e.g., "event:1:meta")
-- KEYS[3]: global stats key ("global:stats")
-- ARGV[1]: timestamp
-- ARGV[2]: purchase ID (UUID)

local ticketKey = KEYS[1]
local metaKey = KEYS[2]
local globalKey = KEYS[3]
local timestamp = ARGV[1]
local purchaseId = ARGV[2]

-- Check if event exists
if redis.call('EXISTS', metaKey) == 0 then
    return {nil, "EVENT_NOT_FOUND"}
end

-- Atomically pop a ticket from the list
local ticket = redis.call('LPOP', ticketKey)

if not ticket then
    return {nil, "NO_TICKETS_AVAILABLE"}
end

-- Update event metadata
local soldCount = redis.call('HINCRBY', metaKey, 'soldTickets', 1)
redis.call('HSET', metaKey, 'lastSoldAt', timestamp)

-- Update global stats
redis.call('HINCRBY', globalKey, 'totalSold', 1)

-- Store purchase record
local purchaseKey = 'purchase:' .. purchaseId
local eventIdFromKey = string.match(ticketKey, 'event:(%d+):tickets')
redis.call('HSET', purchaseKey, 
    'ticketId', ticket,
    'eventId', eventIdFromKey,
    'purchaseId', purchaseId,
    'timestamp', timestamp,
    'status', 'completed'
)

-- Set expiration for purchase record (24 hours)
redis.call('EXPIRE', purchaseKey, 86400)

return {ticket, "SUCCESS", soldCount}