local module_name = ...
local prefix = module_name:match("^(.-)handler$")
local nano = require(prefix .. "nano_ffi")
local kong = kong

local NanoHandler = {}

NanoHandler.PRIORITY = 3000
NanoHandler.VERSION = "1.0.0"

function NanoHandler.init_worker()
    nano.init_attachment()
end

function NanoHandler.access(conf)
    local ctx = kong.ctx.plugin
    
    local headers = kong.request.get_headers()
    local session_id = nano.generate_session_id()
    
    local session_data = nano.init_session(session_id)
    if not session_data then
        kong.ctx.plugin.cleanup_needed = false
        return
    end
    
    ctx.session_data = session_data
    ctx.session_id = session_id
    if nano.is_session_finalized(session_id) then
        kong.log.debug("Session has already been inspected, no need for further inspection")
        return
    end

    local meta_data = nano.handle_start_transaction()
    if not meta_data then
        kong.log.debug("Failed to handle start transaction - failing mode")
        ctx.cleanup_needed = true
        return
    end

    local req_headers = nano.handleHeaders(headers)
    if not req_headers then
        kong.log.debug("Failed to handle request headers - failing mode")
        ctx.cleanup_needed = true
        return
    end

    local has_content_length = tonumber(ngx.var.http_content_length) and tonumber(ngx.var.http_content_length) > 0
    local contains_body = has_content_length and 1 or 0

    local verdict, response = nano.send_data(session_id, session_data, meta_data, req_headers, contains_body, nano.HttpChunkType.HTTP_REQUEST_FILTER)
    if verdict ~= nano.AttachmentVerdict.INSPECT then
        ctx.cleanup_needed = true
        if verdict == nano.AttachmentVerdict.DROP then
            return nano.handle_custom_response(session_data, response)
        end
        return
    end

    if contains_body == 1 then
        local body = kong.request.get_raw_body()
        if body and #body > 0 then
            verdict, response = nano.send_body(session_id, session_data, body, nano.HttpChunkType.HTTP_REQUEST_BODY)
            if verdict ~= nano.AttachmentVerdict.INSPECT then
                ctx.cleanup_needed = true
                if verdict == nano.AttachmentVerdict.DROP then
                    return nano.handle_custom_response(session_data, response)
                end
                return
            end
        else       
            local body_file = ngx.var.request_body_file
            if body_file then
                local file = io.open(body_file, "rb")
                if file then
                    local chunk_size = 8192
                    local chunk_count = 0
                    local start_time = ngx.now()
                    local timeout_sec = nano.get_request_processing_timeout_sec()
                    kong.log.debug("Request body reading timeout set to ", timeout_sec, " seconds")
                    
                    while true do
                        ngx.update_time()
                        local current_time = ngx.now()
                        local elapsed = current_time - start_time
                        
                        if elapsed > timeout_sec then
                            ctx.cleanup_needed = true
                            kong.log.warn("Request body reading timeout after ", elapsed, " seconds")
                            file:close()
                            return
                        end
                        
                        local chunk = file:read(chunk_size)
                        if not chunk or #chunk == 0 then
                            kong.log.debug("End of request body file reached")
                            break
                        end
                        
                        chunk_count = chunk_count + 1
                        kong.log.debug("Sending request body chunk ", chunk_count, " of size ", #chunk, " bytes to C module")
                        verdict, response = nano.send_body(session_id, session_data, chunk, nano.HttpChunkType.HTTP_REQUEST_BODY)
                        
                        if verdict ~= nano.AttachmentVerdict.INSPECT then
                            file:close()
                            ctx.cleanup_needed = true
                            if verdict == nano.AttachmentVerdict.DROP then
                                return nano.handle_custom_response(session_data, response)
                            end
                            return
                        end
                    end
                    file:close()
                    kong.log.debug("Sent ", chunk_count, " chunks from request body file")
                end
            else
                kong.log.err("Request body expected but no body data or file available")
            end
        end

        local ok, verdict, response = pcall(function()
            return nano.end_inspection(session_id, session_data, nano.HttpChunkType.HTTP_REQUEST_END)
        end)

        if not ok then
            kong.log.debug("Error ending request inspection: ", verdict, " - failing open")
            ctx.cleanup_needed = true
            return
        end

        if verdict ~= nano.AttachmentVerdict.INSPECT then
            ctx.cleanup_needed = true
            if verdict == nano.AttachmentVerdict.DROP then
                return nano.handle_custom_response(session_data, response)
            end
            return
        end
    end
end

function NanoHandler.header_filter(conf)
    local ctx = kong.ctx.plugin
    if nano.is_session_finalized(ctx.session_data) then
        kong.log.debug("Session has already been inspected, no need for further inspection")
        return
    end

    if ctx.cleanup_needed then
        kong.log.debug("cleanup in header_filter, passing through")
        return
    end

    local session_id = ctx.session_id
    local session_data = ctx.session_data

    local headers = kong.response.get_headers()
    local header_data = nano.handleHeaders(headers)
    
    if not header_data then
        kong.log.debug("Failed to handle response headers - failing open")
        ctx.cleanup_needed = true
        return
    end

    local status_code = kong.response.get_status()
    local content_length = tonumber(headers["content-length"]) or 0
    
    local verdict, response = nano.send_response_headers(session_id, session_data, header_data, status_code, content_length)
    if verdict ~= nano.AttachmentVerdict.INSPECT then
        ctx.cleanup_needed = true
        if verdict == nano.AttachmentVerdict.DROP then
            kong.log.debug("DROP verdict in header_filter - sending block response immediately")
            return nano.handle_custom_response(session_data, response)
        end
        ngx.header["Content-Length"] = nil
        return
    end

    ngx.header["Content-Length"] = nil
    
    ctx.expect_body = not (status_code == 204 or status_code == 304 or (100 <= status_code and status_code < 200) or content_length == 0)
end

function NanoHandler.body_filter(conf)
    local ctx = kong.ctx.plugin
    local chunk = ngx.arg[1]
    local eof = ngx.arg[2]
    
    local session_id = ctx.session_id
    local session_data = ctx.session_data
    
    if nano.is_session_finalized(session_data) then
        kong.log.debug("Session has already been inspected, no need for further inspection")
        return
    end
    
    if ctx.cleanup_needed then
        kong.log.debug("cleanup chunk without inspection, passing through")
        return
    end

    if not ctx.body_filter_start_time then
        ctx.body_filter_start_time = ngx.now()
        ctx.body_filter_timeout_sec = nano.get_response_processing_timeout_sec()
        kong.log.debug("body_filter timeout set to ", ctx.body_filter_timeout_sec, " seconds")
    end
    
    local elapsed_time = ngx.now() - ctx.body_filter_start_time
    if elapsed_time > ctx.body_filter_timeout_sec then
        kong.log.warn("Body filter timeout after ", elapsed_time, " seconds - failing open")
        ctx.cleanup_needed = true
        return
    end

    if chunk and #chunk > 0 then
        ctx.body_buffer_chunk = ctx.body_buffer_chunk or 0
        ctx.body_seen = true

        local verdict, response, modifications = nano.send_body(session_id, session_data, chunk, nano.HttpChunkType.HTTP_RESPONSE_BODY)
        
        if modifications then
            chunk = nano.handle_body_modifications(chunk, modifications, ctx.body_buffer_chunk)
        end

        ctx.body_buffer_chunk = ctx.body_buffer_chunk + 1

        if verdict ~= nano.AttachmentVerdict.INSPECT then
            ctx.cleanup_needed = true
            if verdict == nano.AttachmentVerdict.DROP then
                kong.log.debug("DROP verdict during response streaming - closing connection")
                ngx.header["Connection"] = "close"
                ngx.arg[1] = ""
                ngx.arg[2] = true
                return
            end
        end
        
        ngx.arg[1] = chunk
        return
    end

    if eof then
        if ctx.body_seen or ctx.expect_body == false then
            ctx.cleanup_needed = true
            local verdict, response = nano.end_inspection(session_id, session_data, nano.HttpChunkType.HTTP_RESPONSE_END)
            if verdict ~= nano.AttachmentVerdict.INSPECT then
                kong.log.debug("Final verdict after end_inspection: ", verdict)
                ctx.cleanup_needed = true
                if verdict == nano.AttachmentVerdict.DROP then
                    kong.log.debug("DROP verdict at EOF - closing connection")
                    ngx.header["Connection"] = "close"
                    ngx.arg[1] = ""
                    ngx.arg[2] = true
                    return
                end
            end
        end
        
    end
end

function NanoHandler.log(conf)
    local ctx = kong.ctx.plugin
    if ctx.cleanup_needed then
        nano.fini_session(ctx.session_data)
        nano.cleanup_all()
        ctx.session_data = nil
        ctx.session_id = nil
        collectgarbage("collect")
    end
end

return NanoHandler