--
-- Licensed to the Apache Software Foundation (ASF) under one or more
-- contributor license agreements.  See the NOTICE file distributed with
-- this work for additional information regarding copyright ownership.
-- The ASF licenses this file to You under the Apache License, Version 2.0
-- (the "License"); you may not use this file except in compliance with
-- the License.  You may obtain a copy of the License at
--
--     http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
--
local core = require("apisix.core")
local dbg = require("apisix.inspect.dbg")
local lfs = require("lfs")
local pl_path = require("pl.path")
local io = io
local table_insert = table.insert
local pcall = pcall
local ipairs = ipairs
local os = os
local ngx = ngx
local loadstring = loadstring
local format = string.format

local _M = {}

local last_modified = 0

local stop = false

local running = false

local last_report_time = 0

local REPORT_INTERVAL = 30 -- secs

local function run_lua_file(file)
    local f, err = io.open(file, "rb")
    if not f then
        return false, err
    end
    local code, err = f:read("*all")
    f:close()
    if code == nil then
        return false, format("cannot read hooks file: %s", err)
    end
    local func, err = loadstring(code)
    if not func then
        return false, err
    end
    func()
    return true
end

local function setup_hooks(file)
    if pl_path.exists(file) then
        dbg.unset_all()
        local _, err = pcall(run_lua_file, file)
        local hooks = {}
        for _, hook in ipairs(dbg.hooks()) do
            table_insert(hooks, hook.key)
        end
        core.log.warn("set hooks: err: ", err, ", hooks: ", core.json.delay_encode(hooks))
    end
end

local function reload_hooks(premature, delay, file)
    if premature or stop then
        stop = false
        running = false
        return
    end

    local time, err = lfs.attributes(file, 'modification')
    if err then
        if last_modified ~= 0 then
            core.log.info(err, ", disable all hooks")
            dbg.unset_all()
            last_modified = 0
        end
    elseif time ~= last_modified then
        setup_hooks(file)
        last_modified = time
    else
        local ts = os.time()
        if ts - last_report_time >= REPORT_INTERVAL then
            local hooks = {}
            for _, hook in ipairs(dbg.hooks()) do
                table_insert(hooks, hook.key)
            end
            core.log.info("alive hooks: ", core.json.encode(hooks))
            last_report_time = ts
        end
    end

    local ok, err = ngx.timer.at(delay, reload_hooks, delay, file)
    if not ok then
        core.log.error("failed to create the timer: ", err)
        running = false
    end
end

function _M.init(delay, file)
    if not running then
        file = file or "/usr/local/apisix/plugin_inspect_hooks.lua"
        delay = delay or 3

        setup_hooks(file)

        local ok, err = ngx.timer.at(delay, reload_hooks, delay, file)
        if not ok then
            core.log.error("failed to create the timer: ", err)
            return
        end
        running = true
    end
end

function _M.destroy()
    stop = true
end

return _M