local records_key = KEYS[1]
local unique_key = KEYS[2]
local idkeys_key = KEYS[3]
local expiry_key = KEYS[4]
local available_key = KEYS[5]
local inventory_key = KEYS[6]
local owners_key = KEYS[7]
local owner_expiry_key = KEYS[8]
local operation_key = KEYS[9]

local checked_at_ms = tonumber(ARGV[1])
local next_state = ARGV[2]
local latency_ns = tonumber(ARGV[3])
local cleanup_limit = tonumber(ARGV[4])
local operation_ttl_ms = tonumber(ARGV[5])
local proxy_id = ARGV[6]

local committed = redis.call('GET', operation_key)
if committed then
    return committed
end

local function is_managed(state)
    return state == 'FETCHED' or state == 'CHECKING' or state == 'AVAILABLE' or
        state == 'SUSPECT' or state == 'DRAINING'
end

local function decrement_inventory(upstream)
    if not upstream or upstream == '' then
        return
    end
    local value = redis.call('HINCRBY', inventory_key, upstream, -1)
    if value < 0 then
        redis.call('HSET', inventory_key, upstream, 0)
    end
end

local function remove_available(id, record)
    redis.call('ZREM', available_key, id)
    for _, index_key in ipairs(record and record.indexKeys or {}) do
        redis.call('ZREM', index_key, id)
    end
end

local function remove_proxy(id)
    local raw = redis.call('HGET', records_key, id)
    local record = nil
    if raw then
        record = cjson.decode(raw)
        remove_available(id, record)
        if is_managed(record.state) then
            decrement_inventory(record.sourceUpstream)
        end
    else
        redis.call('ZREM', available_key, id)
    end
    local digest = redis.call('HGET', idkeys_key, id)
    if digest and redis.call('HGET', unique_key, digest) == id then
        redis.call('HDEL', unique_key, digest)
    end
    redis.call('HDEL', idkeys_key, id)
    redis.call('HDEL', records_key, id)
    redis.call('ZREM', expiry_key, id)
    redis.call('HDEL', owners_key, id)
    redis.call('ZREM', owner_expiry_key, id)
end

local function cleanup_expired()
    local expired = redis.call('ZRANGEBYSCORE', expiry_key, '-inf', checked_at_ms, 'LIMIT', 0, cleanup_limit)
    for _, id in ipairs(expired) do
        remove_proxy(id)
    end
end

local function touch(key, expires_at_ms)
    if redis.call('EXISTS', key) == 0 then
        return
    end
    local current = redis.call('PEXPIRETIME', key)
    if current < expires_at_ms then
        redis.call('PEXPIREAT', key, expires_at_ms)
    end
end

local function finish(reply, hard_expiry_ms)
    local encoded = cjson.encode(reply)
    redis.call('SET', operation_key, encoded, 'PX', operation_ttl_ms)
    if hard_expiry_ms then
        local operation_expiry_ms = redis.call('PEXPIRETIME', operation_key)
        if operation_expiry_ms > hard_expiry_ms then
            redis.call('PEXPIREAT', operation_key, hard_expiry_ms)
        end
    end
    return encoded
end

local transitions = {
    FETCHED = {CHECKING = true, EXPIRED = true, REMOVED = true},
    CHECKING = {AVAILABLE = true, UNHEALTHY = true, EXPIRED = true, REMOVED = true},
    AVAILABLE = {SUSPECT = true, DRAINING = true, EXTRACTED = true, EXPIRED = true},
    SUSPECT = {AVAILABLE = true, UNHEALTHY = true, DRAINING = true, EXPIRED = true},
    DRAINING = {EXPIRED = true, UNHEALTHY = true, REMOVED = true},
    UNHEALTHY = {CHECKING = true, REMOVED = true, EXPIRED = true},
    EXTRACTED = {EXPIRED = true, REMOVED = true},
    EXPIRED = {REMOVED = true},
    REMOVED = {},
}

cleanup_expired()

local raw = redis.call('HGET', records_key, proxy_id)
if not raw then
    return finish({status = 'not_found'})
end
local record = cjson.decode(raw)
if tonumber(record.expiresAtMs) <= checked_at_ms then
    remove_proxy(proxy_id)
    return finish({status = 'not_found'})
end

local last_checked_at_ms = tonumber(record.lastCheckedAtMs or '0')
if checked_at_ms < last_checked_at_ms then
    return finish({status = 'stale'})
end
if checked_at_ms == last_checked_at_ms then
    if record.state ~= next_state then
        return finish({status = 'stale'})
    end
    return finish({status = 'ok', record = raw}, tonumber(record.expiresAtMs))
end
if record.state ~= next_state and not (transitions[record.state] and transitions[record.state][next_state]) then
    return finish({status = 'invalid'})
end

local was_managed = is_managed(record.state)
local will_be_managed = is_managed(next_state)
remove_available(proxy_id, record)
record.state = next_state
record.lastCheckedAtMs = checked_at_ms
record.latencyNs = latency_ns
if next_state == 'AVAILABLE' then
    record.lastSuccessAtMs = checked_at_ms
end
if was_managed and not will_be_managed then
    decrement_inventory(record.sourceUpstream)
elseif not was_managed and will_be_managed then
    redis.call('HINCRBY', inventory_key, record.sourceUpstream, 1)
end

local encoded = cjson.encode(record)
redis.call('HSET', records_key, proxy_id, encoded)
local owned = (record.ownerWorkerId and record.ownerWorkerId ~= '') or redis.call('HEXISTS', owners_key, proxy_id) == 1
if next_state == 'AVAILABLE' and not owned and tonumber(record.usableUntilMs) > checked_at_ms then
    redis.call('ZADD', available_key, record.usableUntilMs, proxy_id)
    for _, index_key in ipairs(record.indexKeys or {}) do
        redis.call('ZADD', index_key, record.usableUntilMs, proxy_id)
        touch(index_key, tonumber(record.expiresAtMs))
    end
end
touch(records_key, tonumber(record.expiresAtMs))
touch(unique_key, tonumber(record.expiresAtMs))
touch(idkeys_key, tonumber(record.expiresAtMs))
touch(expiry_key, tonumber(record.expiresAtMs))
touch(available_key, tonumber(record.expiresAtMs))
touch(inventory_key, tonumber(record.expiresAtMs))
touch(owners_key, tonumber(record.expiresAtMs))
touch(owner_expiry_key, tonumber(record.expiresAtMs))

return finish({status = 'ok', record = encoded}, tonumber(record.expiresAtMs))