local scope = require 'workspace.scope'
local ws    = require 'workspace'

local collect    = {}
local subscribed = {}

local m = {}

--- 订阅一个名字
---@param uri uri
---@param name string
---@param value any
function m.subscribe(uri, name, value)
    -- 订阅部分
    local uriSubscribed = subscribed[uri]
    if not uriSubscribed then
        uriSubscribed = {}
        subscribed[uri] = uriSubscribed
    end
    uriSubscribed[name] = true
    -- 收集部分
    local nameCollect = collect[name]
    if not nameCollect then
        nameCollect = {}
        collect[name] = nameCollect
    end
    if value == nil then
        value = true
    end
    nameCollect[uri] = value
end

--- 丢弃掉某个 uri 中收集的所有信息
---@param uri uri
function m.dropUri(uri)
    local uriSubscribed = subscribed[uri]
    if not uriSubscribed then
        return
    end
    subscribed[uri] = nil
    for name in pairs(uriSubscribed) do
        collect[name][uri] = nil
    end
end

--- 是否包含某个名字的订阅
---@param name string
---@return boolean
function m.has(name)
    local nameCollect = collect[name]
    if not nameCollect then
        return false
    end
    if next(nameCollect) == nil then
        collect[name] = nil
        return false
    end
    return true
end

local DUMMY_FUNCTION = function () end

---@param scp scope
local function eachOfFolder(nameCollect, scp)
    local curi, value

    local function getNext()
        curi, value = next(nameCollect, curi)
        if not curi then
            return nil, nil
        end
        if scp:isChildUri(curi)
        or scp:isLinkedUri(curi) then
            return value, curi
        end
        return getNext()
    end

    return getNext
end

---@param scp scope
local function eachOfLinked(nameCollect, scp)
    local curi, value

    local function getNext()
        curi, value = next(nameCollect, curi)
        if not curi then
            return nil, nil
        end
        if  scp:isChildUri(curi)
        and scp:isLinkedUri(curi) then
            return value, curi
        end

        local cscp =   scope.getFolder(curi)
                    or scope.getLinkedScope(curi)
                    or scope.fallback

        if cscp == scp
        or cscp:isChildUri(scp.uri)
        or cscp:isLinkedUri(scp.uri) then
            return value, curi
        end

        return getNext()
    end

    return getNext
end

---@param scp scope
local function eachOfFallback(nameCollect, scp)
    local curi, value

    local function getNext()
        curi, value = next(nameCollect, curi)
        if not curi then
            return nil, nil
        end
        if scp:isLinkedUri(curi) then
            return value, curi
        end

        local cscp =   scope.getFolder(curi)
                    or scope.getLinkedScope(curi)
                    or scope.fallback

        if cscp == scp then
            return value, curi
        end

        return getNext()
    end

    return getNext
end

--- 迭代某个名字的订阅
---@param uri  uri
---@param name string
function m.each(uri, name)
    local nameCollect = collect[name]
    if not nameCollect then
        return DUMMY_FUNCTION
    end

    local scp = scope.getFolder(uri)

    if scp then
        return eachOfFolder(nameCollect, scp)
    end

    scp = scope.getLinkedScope(uri)

    if scp then
        return eachOfLinked(nameCollect, scp)
    end

    return eachOfFallback(nameCollect, scope.fallback)
end

return m