MediaAdapter = {}

local function trim(value, maxLength)
    local text = tostring(value or ''):match('^%s*(.-)%s*$')
    if maxLength and #text > maxLength then
        text = text:sub(1, maxLength)
    end
    return text
end

local function extensionFromUrl(url)
    return tostring(url or ''):match('%.([%w]+)%??[^/]*$')
end

local function extensionFromName(name)
    return tostring(name or ''):match('%.([%w]+)$')
end

local function isAllowedExtension(ext)
    ext = tostring(ext or ''):lower()
    for _, allowed in ipairs(Config.Media.allowedExtensions or {}) do
        if ext == allowed then
            return true
        end
    end
    return false
end

local function mimeExtension(mime)
    return ({
        ['image/jpeg'] = 'jpg',
        ['image/jpg'] = 'jpg',
        ['image/png'] = 'png'
    })[tostring(mime or ''):lower()]
end

local function urlEncode(value)
    return tostring(value or ''):gsub('\n', '\r\n'):gsub('([^%w%-_%.~])', function(char)
        return string.format('%%%02X', string.byte(char))
    end)
end

local function decodeJson(value)
    if not value or value == '' then return nil end
    local ok, result = pcall(json.decode, value)
    if ok then return result end
    return nil
end

function MediaAdapter.IsAllowedExternalUrl(url)
    url = tostring(url or '')
    if Config.Media.requireHttps and not url:match('^https://') then
        return false, 'url_must_be_https'
    end

    if url:match('^https://i%.ibb%.co/') or url:match('^https://ibb%.co/') then
        return true
    end

    local ext = extensionFromUrl(url)
    if not ext then return false, 'missing_extension' end
    ext = ext:lower()

    if isAllowedExtension(ext) then return true end
    return false, 'unsupported_extension'
end

function MediaAdapter.ValidateUpload(payload)
    if type(payload) ~= 'table' then return false, 'invalid_payload' end

    local name = trim(payload.name, 180)
    local mime = trim(payload.mime, 80):lower()
    local data = tostring(payload.data or '')
    local size = tonumber(payload.size) or 0

    if data == '' then return false, 'missing_data' end
    if size <= 0 then return false, 'missing_size' end
    if size > (Config.Media.maxBytes or 2097152) then return false, 'file_too_large' end

    local ext = extensionFromName(name) or mimeExtension(mime)
    if not isAllowedExtension(ext) then return false, 'unsupported_extension' end
    if mimeExtension(mime) and not isAllowedExtension(mimeExtension(mime)) then return false, 'unsupported_mime' end

    return true, {
        name = name ~= '' and name or ('bleeter_%s.%s'):format(os.time(), ext),
        mime = mime,
        data = data,
        size = size,
        extension = ext
    }
end

function MediaAdapter.Upload(payload, cb)
    local ok, upload = MediaAdapter.ValidateUpload(payload)
    if not ok then
        cb(false, upload)
        return
    end

    if Config.Media.provider ~= 'imgbb' then
        cb(false, 'provider_not_configured')
        return
    end

    -- Erst die Konsolenvariable, dann die Config. So bleibt der Schluessel
    -- aus der Versionsverwaltung heraus.
    local apiKey = trim(GetConvar('bleeter_imgbb_key', Config.Media.imgbbApiKey or ''))
    if apiKey == '' then
        cb(false, 'missing_imgbb_key')
        return
    end

    local body = ('image=%s&name=%s'):format(urlEncode(upload.data), urlEncode(upload.name))
    local url = ('https://api.imgbb.com/1/upload?key=%s'):format(urlEncode(apiKey))

    PerformHttpRequest(url, function(statusCode, responseText)
        if statusCode < 200 or statusCode >= 300 then
            cb(false, 'upload_failed')
            return
        end

        local decoded = decodeJson(responseText)
        local data = decoded and decoded.data
        local imageUrl = data and (data.url or data.display_url)

        if not imageUrl or imageUrl == '' then
            cb(false, 'missing_upload_url')
            return
        end

        cb(true, {
            url = imageUrl,
            deleteUrl = data.delete_url,
            size = upload.size,
            mime = upload.mime,
            name = upload.name
        })
    end, 'POST', body, {
        ['Content-Type'] = 'application/x-www-form-urlencoded'
    })
end