-- WARNING: if you cause errors during configuration reload by putting
-- incompatible data into the table returned by mcp_config_pools, the daeomon
-- will exit.
-- TODO: fallback cache for broken/overloaded zones.

-- local zone could/should be fetched from environment or local file.
-- doing so allows all configuration files to be identical, simplifying consistency checks.
local my_zone = 'z1'

local STAT_EXAMPLE <const> = 1
local STAT_ANOTHER <const> = 2

function mcp_config_pools(oldss)
    mcp.add_stat(STAT_EXAMPLE, "example")
    mcp.add_stat(STAT_ANOTHER, "another")
    --mcp.tcp_keepalive(true)
    mcp.backend_connect_timeout(5.5) -- 5 and a half second timeout.
    -- alias mcp.backend for convenience.
    -- important to alias global variables in routes where speed is concerned.
    local srv = mcp.backend
    -- local zones = { 'z1', 'z2', 'z3' }

    -- IPs are "127" . "zone" . "pool" . "srv"
    local pfx = 'fooz1'
    local fooz1 = {
        srv(pfx .. 'srv1', '127.1.1.1', 11212),
        srv(pfx .. 'srv2', '127.1.1.2', 11212),
        srv(pfx .. 'srv3', '127.1.1.3', 11212),
    }
    pfx = 'fooz2'
    local fooz2 = {
        srv(pfx .. 'srv1', '127.2.1.1', 11213),
        srv(pfx .. 'srv2', '127.2.1.2', 11213),
        srv(pfx .. 'srv3', '127.2.1.3', 11213),
    }
    pfx = 'fooz3'
    local fooz3 = {
        srv(pfx .. 'srv1', '127.3.1.1', 11214),
        srv(pfx .. 'srv2', '127.3.1.2', 11214),
        srv(pfx .. 'srv3', '127.3.1.3', 11214),
    }

    pfx = 'barz1'
    -- zone "/bar/"-s primary zone should fail; all down.
    local barz1 = {
        srv(pfx .. 'srv1', '127.1.2.1', 11210),
        srv(pfx .. 'srv2', '127.1.2.2', 11210),
        srv(pfx .. 'srv3', '127.1.2.3', 11210),
    }
    pfx = 'barz2'
    local barz2 = {
        srv(pfx .. 'srv1', '127.2.2.1', 11215),
        srv(pfx .. 'srv2', '127.2.2.2', 11215),
        srv(pfx .. 'srv3', '127.2.2.3', 11215),
    }
    pfx = 'barz3'
    local barz3 = {
        srv(pfx .. 'srv1', '127.3.2.1', 11216),
        srv(pfx .. 'srv2', '127.3.2.2', 11216),
        srv(pfx .. 'srv3', '127.3.2.3', 11216),
    }

    -- fallback cache for any zone
    -- NOT USED YET
    pfx = 'fallz1'
    local fallz1 = {
        srv(pfx .. 'srv1', '127.0.2.1', 11212),
    }
    pfx = 'fallz2'
    local fallz2 = {
        srv(pfx .. 'srv1', '127.0.2.2', 11212),
    }
    pfx = 'fallz3'
    local fallz3 = {
        srv(pfx .. 'srv1', '127.0.2.3', 11212),
    }

    local main_zones = {
        foo = { z1 = fooz1, z2 = fooz2, z3 = fooz3 },
        bar = { z1 = barz1, z2 = barz2, z3 = barz3 },
        -- fall = { z1 = fallz1, z2 = fallz2, z3 = fallz3 },
    }

    -- FIXME: should we copy the table to keep the pool tables around?
    -- does the hash selector hold a reference to the pool (but only available in main config?)

    -- convert the pools into hash selectors.
    -- TODO: is this a good place to add prefixing/hash editing?
    for _, subs in pairs(main_zones) do
        for k, v in pairs(subs) do
            -- next line uses a ring hash in "evcache compat" mode. note the
            -- hash= override to use MD5 key hashing from ketama.
            -- subs[k] = mcp.pool(v, { dist = mcp.dist_ring_hash, omode = "evcache", hash = mcp.dist_ring_hash.hash })
            -- override the number of buckets per server.
            -- subs[k] = mcp.pool(v, { dist = mcp.dist_ring_hash, omode = "evcache", hash = mcp.dist_ring_hash.hash, obuckets = 240 })
            -- this line uses the default (currently xxhash + jump hash)
            subs[k] = mcp.pool(v)

            -- use this next line instead for jump hash.
            -- the order of servers in the pool argument _must_ not change!
            -- adding the seed string will give a different key distribution
            -- for each zone.
            -- NOTE: 'k' may not be the right seed here:
            -- instead stitch main_zone's key + the sub key?
            -- subs[k] = mcp.pool(v, { dist = mcp.dist_jump_hash, seed = k })
            -- subs[k] = mcp.pool(v, { dist = mcp.dist_jump_hash, seed = k, filter = "stop", filter_conf = "|#|" })
            -- subs[k] = mcp.pool(v, { dist = mcp.dist_jump_hash, seed = k, filter = "tags", filter_conf = "{}" })
        end
    end

    return main_zones
end

-- WORKER CODE:

-- need to redefine main_zones using fetched selectors?

function reqlog_factory(route)
    local nr = route
    return function(r)
        local res, detail = nr(r)
        mcp.log_req(r, res, detail)
        return res
    end
end

-- TODO: Fallback zone here?
function failover_factory(zones, local_zone)
    local near_zone = zones[local_zone]
    local far_zones = {}
    -- NOTE: could shuffle/sort to re-order zone retry order
    -- or use 'next(far_zones, idx)' via a stored upvalue here
    for k, v in pairs(zones) do
        if k ~= local_zone then
            far_zones[k] = v
        end
    end
    return function(r)
        local res = near_zone(r)
        if res:hit() == false then
            -- example for mcp.log... Don't do this though :)
            -- mcp.log("failed to find " .. r:key() .. " in zone: " .. local_zone)
            --for _, zone in pairs(far_zones) do
            --    res = zone(r)
            local restable = mcp.await(r, far_zones, 1)
            for _, res in pairs(restable) do
                if res:hit() then
                    --break
                    return res, "failover_backup_hit"
                end
            end
            return restable[1], "failover_backup_miss"
        end
        -- example of making a new set request on the side.
        -- local nr = mcp.request("set /foo/asdf 0 0 " .. res:vlen() .. "\r\n", res)
        -- local nr = mcp.request("set /foo/asdf 0 0 2\r\n", "mo\r\n")
        -- near_zone(nr)
        return res, "failover_hit" -- send result back to client
    end
end

function meta_get_factory(zones, local_zone)
    local near_zone = zones[local_zone]
    -- in this test function we only fetch from the local zone.
    return function(r)
        if r:has_flag("l") == true then
            print("client asking for last access time")
        end
        local texists, token = r:flag_token("O")
        -- next example returns the previous token and replaces it.
        -- local texists, token = r:flag_token("O", "Odoot")
        if token ~= nil then
            print("meta opaque flag token: " .. token)
        end
        local res = near_zone(r)

        return res
    end
end

function meta_set_factory(zones, local_zone)
    local near_zone = zones[local_zone]
    -- in this test function we only talk to the local zone.
    return function(r)
        local res = near_zone(r)
        if res:code() == mcp.MCMC_CODE_NOT_FOUND then
            print("got meta NF response")
        end
        print("meta response line: " .. res:line())

        return res
    end
end

-- SET's to main zone, issues deletes to far zones.
function setinvalidate_factory(zones, local_zone)
    local near_zone = zones[local_zone]
    local far_zones = {}
    -- NOTE: could shuffle/sort to re-order zone retry order
    -- or use 'next(far_zones, idx)' via a stored upvalue here
    for k, v in pairs(zones) do
        if k ~= local_zone then
            far_zones[k] = v
        end
    end
    local new_req = mcp.request
    return function(r)
        local res = near_zone(r)
        if res:ok() == true then
            -- create a new delete request
            local dr = new_req("delete /testing/" .. r:key() .. "\r\n")
            -- example of new request from existing request
            -- note this isn't trimming the key so it'll make a weird one.
            -- local dr = new_req("set /bar/" .. r:key() .. " 0 0 " .. r:token(5) .. "\r\n", r)
            -- AWAIT_BACKGROUND allows us to immediately resume processing, executing the
            -- delete requests in the background.
            mcp.await(dr, far_zones, 0, mcp.AWAIT_BACKGROUND)
            --mcp.await(dr, far_zones, 0)
            mcp.log_req(r, res, "setinvalidate") -- time against the original request, since we have no result.
        end
        -- use original response for client, not DELETE's response.
        -- else client won't understand.
        return res -- send result back to client
    end
end

-- NOTE: this function is culling key prefixes. it is an error to use it
-- without a left anchored (^) pattern.
function prefixtrim_factory(pattern, list, default)
    local p = pattern
    local l = list
    local d = default
    local s = mcp.stat
    return function(r)
        local i, j, match = string.find(r:key(), p)
        local route
        if match ~= nil then
            -- remove the key prefix so we don't waste storage.
            r:ltrimkey(j)
            route = l[match]
            if route == nil then
                -- example counter: tick when default route hit.
                s(STAT_EXAMPLE, 1)
                return d(r)
            end
        end
        return route(r)
    end
end

function prefix_factory(pattern, list, default)
    local p = pattern
    local l = list
    local d = default
    local s = mcp.stat
    return function(r)
        local route = l[string.match(r:key(), p)]
        if route == nil then
            -- example counter: tick when default route hit.
            s(STAT_EXAMPLE, 1)
            return d(r)
        end
        return route(r)
    end
end

-- TODO: Check tail call requirements?
function command_factory(map, default)
    local m = map
    local d = default
    return function(r)
        local f = map[r:command()]
        if f == nil then
            -- print("default command")
            return d(r)
        end
        -- testing options replacement...
        -- if r:command() == mcp.CMD_SET then
        --    r:token(4, "100") -- set exptime.
        -- end
        -- print("override command")
        return f(r)
    end
end

-- TODO: is the return value the average? anything special?
-- walks a list of selectors and repeats the request.
function walkall_factory(pool)
    local p = {}
    -- TODO: a shuffle could be useful here.
    for _, v in pairs(pool) do
        table.insert(p, v)
    end
    local x = #p
    return function(r)
        local restable = mcp.await(r, p)
        -- walk results and return "best" result
        -- print("length of await result table", #restable)
        for _, res in pairs(restable) do
            if res:ok() then
                return res
            end
        end
        -- else we return the first result.
        return restable[1]
    end
end

function mcp_config_routes(main_zones)
    -- generate the prefix routes from zones.
    local prefixes = {}
    for pfx, z in pairs(main_zones) do
        local failover = reqlog_factory(failover_factory(z, my_zone))
        local all = walkall_factory(main_zones[pfx])
        local setdel = setinvalidate_factory(z, my_zone)
        local map = {}
        map[mcp.CMD_SET] = all
        -- NOTE: in t/proxy.t all the backends point to the same place
        -- which makes replicating delete return NOT_FOUND
        map[mcp.CMD_DELETE] = all
        -- similar with ADD. will get an NOT_STORED back.
        -- need better routes designed for the test suite (edit the key
        -- prefix or something)
        map[mcp.CMD_ADD] = failover_factory(z, my_zone)
        map[mcp.CMD_MG] = meta_get_factory(z, my_zone)
        map[mcp.CMD_MS] = meta_set_factory(z, my_zone)
        prefixes[pfx] = command_factory(map, failover)
    end

    local routetop = prefix_factory("^/(%a+)/", prefixes, function(r) return "SERVER_ERROR no route\r\n" end)

    -- internally run parser at top of tree
    -- also wrap the request string with a convenience object until the C bits
    -- are attached to the internal parser.
    --mcp.attach(mcp.CMD_ANY, function (r) return routetop(r) end)
    mcp.attach(mcp.CMD_ANY_STORAGE, routetop)
    -- tagged top level attachments. ex: memcached -l tag[tagtest]:127.0.0.1:11212
    -- mcp.attach(mcp.CMD_ANY_STORAGE, function (r) return "SERVER_ERROR no route\r\n" end, "tagtest")
    -- mcp.attach(mcp.CMD_ANY_STORAGE, function (r) return "SERVER_ERROR my route\r\n" end, "newtag")
end