local https = require 'ssl.https'

local internet = {}

--------------------------------------------------------------------------------
-- Util

local SCANDI_SYMBOLS = { 'æ', 'Æ', 'ø', 'Ø', 'å', 'Å' }

local function string_contains_scandi (str)
    for _, symbol in ipairs(SCANDI_SYMBOLS) do
        if topic:match(symbol) then  return  true  end
    end
    return false
end

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local function search_clearbit_for_logo (topic)
    if not (type(topic) == 'string' and topic == topic:lower() and #topic > 0) then
        return nil, 'Bad topic: '..tostring(topic)
    elseif string_contains_scandi(topic) then
        return nil, 'Clearbit does not like æøå: '..tostring(topic)
    end
    --
    for _, domain in ipairs { 'org', 'com', 'net', 'dk' } do
        local search_url  =  ('https://logo-core.clearbit.com/%s.%s'):format(topic, domain)
        local _, code, headers, status  =  https.request { url = search_url, method = 'HEAD' }
        if code == 200 then  return search_url  end
    end
end

local function search_splashbase_for_image_topic (topic)
    if not (type(topic) == 'string' and topic == topic:lower() and #topic > 0) then
        return nil, 'Bad topic: '..tostring(topic)
    elseif string_contains_scandi(topic) then
        return nil, 'Splashbase does not like æøå: '..tostring(topic)
    end

    local search_url  =  string.format('http://www.splashbase.co/api/v1/images/search?query=%s', topic:gsub('%s', '%%20'))
    local body, code, headers, status  =  https.request(search_url)
    if not body then  error(code)  end
    local data = json.decode(body)

    if not data          then  return nil, 'JSON could not decode data for '..topic  end
    if #data.images <= 0 then  return nil, 'Query returned no data for '..topic      end

    local img_url  =  data.images[math.random(#data.images)].url
    assert(type(img_url) == 'string')
    return img_url
end

local WIKIPEDIA_API_URL  =  'https://%s.wikipedia.org/w/api.php?action=query&titles=%s&prop=pageimages&format=json&piprop=original&redirects=1'

local function search_wikipedia_for_images (topics, language, topic_to_image_url)
    if type(topics) == 'string' then  topics = { topics }  end
    local language = language or 'en'
    local topic_to_image_url  =  topic_to_image_url or {}
    --
    local titles_field  =  table.concat(topics, '|'):gsub('%s+', '%%20')

    local body, code, headers, status  =  https.request(WIKIPEDIA_API_URL:format(language, titles_field))
    if not body then  error(code)  end
    local data = json.decode(body)

    if not data then  return {}, 'JSON could not decode data from wikipedia for '..titles_field  end

    -- Determine if some topic was redirected
    local redirected_topics = {}
    for _, redirect in pairs(data.query.normalized or {}) do
        redirected_topics[ redirect.to ]  =  redirected_topics[ redirect.from ] or redirect.from
    end
    for _, redirect in pairs(data.query.redirects or {}) do
        redirected_topics[ redirect.to ]  =  redirected_topics[ redirect.from ] or redirect.from
    end

    -- Determine topic to image
    for _, page in pairs(data.query.pages) do
        local orig_title  =  redirected_topics[ page.title ]
        if not topic_to_image_url[orig_title] then
            local found_url  = false
            if page.original then  found_url  =  page.original.source  end
            topic_to_image_url[orig_title]  =  found_url
        end
    end
    ---
    return topic_to_image_url
end

local function all_topics_has_image (topic_to_image_url)
    for _, url in pairs(topic_to_image_url) do
        if not url then  return false  end
    end
    return true
end

function internet.search_images (topics)
    assert(type(topics) == 'table')
    if #topics == 0 then  return {}  end
    local topic_to_image_url  =  {}
    -- Wikipedia
    search_wikipedia_for_images(topics, 'da', topic_to_image_url)
    if not all_topics_has_image(topic_to_image_url) then  return topic_to_image_url  end
    search_wikipedia_for_images(topics, 'en', topic_to_image_url)
    -- Logoes
    for topic, val in pairs(topic_to_image_url) do
        if not val then
            topic_to_image_url[topic]  =  search_clearbit_for_logo(topic:lower())
        end
    end
    -- Stock photoes
    for topic, val in pairs(topic_to_image_url) do
        if not val then
            topic_to_image_url[topic]  =  search_splashbase_for_image_topic(topic:lower())
        end
    end
    -- Ret
    return topic_to_image_url
end

--------------------------------------------------------------------------------

function internet.download_file (url, filename)
    -- retrieve the content of a URL
    local body, code  =  https.request(url)
    if not body then error(code) end

    -- save the content to a file
    local f = assert(io.open(filename, 'wb'))   -- open in "binary" mode
    f:write(body)
    f:close()
end

--------------------------------------------------------------------------------

return internet