package adk

import (
	"context"
	"fmt"
	"strings"
	"sync/atomic"

	"ai-agent-scaffold-go/internal/domain/agent/model"
	"ai-agent-scaffold-go/internal/domain/agent/ports"
	"google.golang.org/adk/plugin"
	"google.golang.org/adk/plugin/loggingplugin"
)

const maxToolCallIterations = 4

type Factory struct {
	sessionCounter atomic.Uint64
	plugins        map[string]func() (ports.RunnerPlugin, error)
	router         ports.ToolRouter
}

type Agent struct {
	name        string
	kind        string
	description string
	instruction string
	outputKey   string
	chatModel   ports.ChatModel
	router      ports.ToolRouter
	subAgents   []ports.Agent
}

type Runner struct {
	appName string
	agent   ports.Agent
	plugins []ports.RunnerPlugin
	counter *atomic.Uint64
}

func NewFactory() *Factory {
	return &Factory{plugins: defaultPlugins()}
}

func (f *Factory) UseToolRouter(router ports.ToolRouter) {
	f.router = router
}

func (f *Factory) NewLLMAgent(_ context.Context, config model.AgentConfig, chatModel ports.ChatModel) (ports.Agent, error) {
	if strings.TrimSpace(config.Name) == "" {
		return nil, fmt.Errorf("agent name is required")
	}
	if chatModel == nil {
		return nil, fmt.Errorf("agent %q requires a chat model", config.Name)
	}
	return &Agent{
		name:        config.Name,
		kind:        "llm",
		description: config.Description,
		instruction: config.Instruction,
		outputKey:   config.OutputKey,
		chatModel:   chatModel,
		router:      f.router,
	}, nil
}

func (f *Factory) NewLoopAgent(_ context.Context, config model.AgentWorkflowConfig, subAgents []ports.Agent) (ports.Agent, error) {
	return newWorkflowAgent("loop", config, subAgents, f.router)
}

func (f *Factory) NewParallelAgent(_ context.Context, config model.AgentWorkflowConfig, subAgents []ports.Agent) (ports.Agent, error) {
	return newWorkflowAgent("parallel", config, subAgents, f.router)
}

func (f *Factory) NewSequentialAgent(_ context.Context, config model.AgentWorkflowConfig, subAgents []ports.Agent) (ports.Agent, error) {
	return newWorkflowAgent("sequential", config, subAgents, f.router)
}

func (f *Factory) NewRunner(_ context.Context, appName string, agent ports.Agent, pluginNames []string) (model.Runner, error) {
	if strings.TrimSpace(appName) == "" {
		return nil, fmt.Errorf("app name is required")
	}
	if agent == nil {
		return nil, fmt.Errorf("agent is required")
	}
	plugins, err := f.resolvePlugins(pluginNames)
	if err != nil {
		return nil, err
	}
	return &Runner{appName: appName, agent: agent, plugins: plugins, counter: &f.sessionCounter}, nil
}

func newWorkflowAgent(kind string, config model.AgentWorkflowConfig, subAgents []ports.Agent, router ports.ToolRouter) (ports.Agent, error) {
	if strings.TrimSpace(config.Name) == "" {
		return nil, fmt.Errorf("%s agent name is required", kind)
	}
	return &Agent{
		name:        config.Name,
		kind:        kind,
		description: config.Description,
		subAgents:   subAgents,
		router:      router,
	}, nil
}

func (a *Agent) Name() string {
	return a.name
}

func (a *Agent) Description() string {
	return a.description
}

func (a *Agent) run(ctx context.Context, content model.ChatContent) (string, error) {
	return a.runWithVars(ctx, content, map[string]string{})
}

func (a *Agent) runWithVars(ctx context.Context, content model.ChatContent, vars map[string]string) (string, error) {
	switch a.kind {
	case "llm":
		return a.runLLM(ctx, content, vars)
	case "sequential":
		return a.runSequential(ctx, content, vars)
	case "loop", "parallel":
		return a.runFanOut(ctx, content, vars)
	default:
		return "", fmt.Errorf("agent %q has unknown kind %q", a.name, a.kind)
	}
}

func (a *Agent) stream(ctx context.Context, content model.ChatContent, out chan<- string) error {
	switch a.kind {
	case "llm":
		return a.streamLLM(ctx, content, out, map[string]string{})
	default:
		text, err := a.run(ctx, content)
		if err != nil {
			return err
		}
		if text != "" {
			select {
			case out <- text:
			case <-ctx.Done():
				return ctx.Err()
			}
		}
		return nil
	}
}

func (a *Agent) runLLM(ctx context.Context, content model.ChatContent, vars map[string]string) (string, error) {
	messages := initialMessages(applyVars(a.instruction, vars), firstText(content))
	for iter := 0; iter < maxToolCallIterations; iter++ {
		reply, err := a.chatModel.Generate(ctx, messages)
		if err != nil {
			return "", err
		}
		if len(reply.ToolCalls) == 0 {
			return reply.Content, nil
		}
		messages = append(messages, ports.ChatMessage{Role: ports.ChatRoleAssistant, Content: reply.Content, ToolCalls: reply.ToolCalls})
		toolMessages, err := a.executeToolCalls(ctx, reply.ToolCalls)
		if err != nil {
			return "", err
		}
		messages = append(messages, toolMessages...)
	}
	return "", fmt.Errorf("agent %q exceeded tool-call iteration limit %d", a.name, maxToolCallIterations)
}

func (a *Agent) streamLLM(ctx context.Context, content model.ChatContent, out chan<- string, vars map[string]string) error {
	messages := initialMessages(applyVars(a.instruction, vars), firstText(content))
	for iter := 0; iter < maxToolCallIterations; iter++ {
		events, errs := a.chatModel.Stream(ctx, messages)
		var (
			finalText strings.Builder
			toolCalls []ports.ChatToolCall
			done      bool
		)
		streamErr := error(nil)
	streamLoop:
		for {
			select {
			case <-ctx.Done():
				streamErr = ctx.Err()
				break streamLoop
			case ev, ok := <-events:
				if !ok {
					break streamLoop
				}
				if ev.Done {
					done = true
				}
				if ev.Delta != "" {
					finalText.WriteString(ev.Delta)
					select {
					case out <- ev.Delta:
					case <-ctx.Done():
						streamErr = ctx.Err()
						break streamLoop
					}
				}
				if len(ev.ToolCalls) > 0 {
					toolCalls = append(toolCalls, ev.ToolCalls...)
				}
			case err, ok := <-errs:
				if ok && err != nil {
					streamErr = err
				}
				break streamLoop
			}
		}
		if streamErr != nil {
			return streamErr
		}
		if len(toolCalls) == 0 {
			if !done {
				return fmt.Errorf("agent %q stream closed without completion", a.name)
			}
			return nil
		}
		messages = append(messages, ports.ChatMessage{Role: ports.ChatRoleAssistant, Content: finalText.String(), ToolCalls: toolCalls})
		toolMessages, err := a.executeToolCalls(ctx, toolCalls)
		if err != nil {
			return err
		}
		messages = append(messages, toolMessages...)
	}
	return fmt.Errorf("agent %q exceeded tool-call iteration limit %d", a.name, maxToolCallIterations)
}

func (a *Agent) executeToolCalls(ctx context.Context, calls []ports.ChatToolCall) ([]ports.ChatMessage, error) {
	if a.router == nil {
		return nil, fmt.Errorf("agent %q has no tool router but model requested tool calls", a.name)
	}
	out := make([]ports.ChatMessage, 0, len(calls))
	for _, call := range calls {
		result, err := a.router.CallTool(ctx, call.Name, call.Arguments)
		if err != nil {
			return nil, fmt.Errorf("tool %q: %w", call.Name, err)
		}
		out = append(out, ports.ChatMessage{
			Role:       ports.ChatRoleTool,
			Content:    result,
			ToolCallID: call.ID,
			Name:       call.Name,
		})
	}
	return out, nil
}

func (a *Agent) runSequential(ctx context.Context, content model.ChatContent, vars map[string]string) (string, error) {
	scope := cloneVars(vars)
	var last string
	for _, sub := range a.subAgents {
		impl, ok := sub.(*Agent)
		if !ok {
			return "", fmt.Errorf("sub-agent %q is not a runnable agent", sub.Name())
		}
		text, err := impl.runWithVars(ctx, content, scope)
		if err != nil {
			return "", err
		}
		last = text
		if key := strings.TrimSpace(impl.outputKey); key != "" {
			scope[key] = text
		}
	}
	return last, nil
}

func (a *Agent) runFanOut(ctx context.Context, content model.ChatContent, vars map[string]string) (string, error) {
	parts := make([]string, 0, len(a.subAgents))
	for _, sub := range a.subAgents {
		impl, ok := sub.(*Agent)
		if !ok {
			return "", fmt.Errorf("sub-agent %q is not a runnable agent", sub.Name())
		}
		text, err := impl.runWithVars(ctx, content, vars)
		if err != nil {
			return "", err
		}
		parts = append(parts, fmt.Sprintf("[%s] %s", sub.Name(), text))
	}
	return strings.Join(parts, "\n"), nil
}

func cloneVars(vars map[string]string) map[string]string {
	out := make(map[string]string, len(vars)+4)
	for k, v := range vars {
		out[k] = v
	}
	return out
}

func applyVars(template string, vars map[string]string) string {
	if template == "" || len(vars) == 0 {
		return template
	}
	out := template
	for k, v := range vars {
		out = strings.ReplaceAll(out, "{"+k+"}", v)
	}
	return out
}

func initialMessages(instruction, userText string) []ports.ChatMessage {
	messages := make([]ports.ChatMessage, 0, 2)
	if strings.TrimSpace(instruction) != "" {
		messages = append(messages, ports.ChatMessage{Role: ports.ChatRoleSystem, Content: instruction})
	}
	messages = append(messages, ports.ChatMessage{Role: ports.ChatRoleUser, Content: userText})
	return messages
}

func (r *Runner) CreateSession(userID string) (string, error) {
	if strings.TrimSpace(userID) == "" {
		return "", fmt.Errorf("user id is required")
	}
	next := r.counter.Add(1)
	return fmt.Sprintf("%s:%s:%d", r.appName, userID, next), nil
}

func (r *Runner) Run(userID, sessionID string, content model.ChatContent) ([]string, error) {
	if strings.TrimSpace(userID) == "" || strings.TrimSpace(sessionID) == "" {
		return nil, fmt.Errorf("user id and session id are required")
	}
	if err := r.notifyPlugins(userID, sessionID, content); err != nil {
		return nil, err
	}
	impl, ok := r.agent.(*Agent)
	if !ok {
		return nil, fmt.Errorf("runner agent %q is not runnable", r.agent.Name())
	}
	output, err := impl.run(context.Background(), content)
	if err != nil {
		return nil, err
	}
	if output == "" {
		return []string{}, nil
	}
	return []string{output}, nil
}

func (r *Runner) Stream(userID, sessionID string, content model.ChatContent) (<-chan string, <-chan error) {
	outputs := make(chan string, 8)
	errs := make(chan error, 1)
	go func() {
		defer close(outputs)
		defer close(errs)
		if strings.TrimSpace(userID) == "" || strings.TrimSpace(sessionID) == "" {
			errs <- fmt.Errorf("user id and session id are required")
			return
		}
		if err := r.notifyPlugins(userID, sessionID, content); err != nil {
			errs <- err
			return
		}
		impl, ok := r.agent.(*Agent)
		if !ok {
			errs <- fmt.Errorf("runner agent %q is not runnable", r.agent.Name())
			return
		}
		if err := impl.stream(context.Background(), content, outputs); err != nil {
			errs <- err
		}
	}()
	return outputs, errs
}

func (r *Runner) notifyPlugins(userID, sessionID string, content model.ChatContent) error {
	for _, item := range r.plugins {
		if err := item.OnUserMessage(context.Background(), r.appName, userID, sessionID, r.agent, content); err != nil {
			return fmt.Errorf("plugin %q on user message: %w", item.Name(), err)
		}
		if err := item.BeforeAgent(context.Background(), r.appName, userID, sessionID, r.agent); err != nil {
			return fmt.Errorf("plugin %q before agent: %w", item.Name(), err)
		}
	}
	return nil
}

func firstText(content model.ChatContent) string {
	if len(content.Texts) == 0 {
		return ""
	}
	return content.Texts[0].Message
}

func defaultPlugins() map[string]func() (ports.RunnerPlugin, error) {
	return map[string]func() (ports.RunnerPlugin, error){
		"myTestPlugin": newMyTestPlugin,
		"myLogPlugin": func() (ports.RunnerPlugin, error) {
			p, err := loggingplugin.New("myLogPlugin")
			if err != nil {
				return nil, err
			}
			return adkRunnerPlugin{name: "myLogPlugin", plugin: p}, nil
		},
	}
}

func (f *Factory) resolvePlugins(names []string) ([]ports.RunnerPlugin, error) {
	if len(names) == 0 {
		return nil, nil
	}
	plugins := make([]ports.RunnerPlugin, 0, len(names))
	for _, name := range names {
		pluginName := strings.TrimSpace(name)
		if pluginName == "" {
			continue
		}
		builder, ok := f.plugins[pluginName]
		if !ok {
			return nil, fmt.Errorf("runner plugin %q is not registered", pluginName)
		}
		plugin, err := builder()
		if err != nil {
			return nil, fmt.Errorf("create runner plugin %q: %w", pluginName, err)
		}
		plugins = append(plugins, plugin)
	}
	return plugins, nil
}

func newMyTestPlugin() (ports.RunnerPlugin, error) {
	return myTestPlugin{}, nil
}

type myTestPlugin struct{}

func (myTestPlugin) Name() string {
	return "myTestPlugin"
}

func (myTestPlugin) OnUserMessage(_ context.Context, _, _, _ string, _ ports.Agent, content model.ChatContent) error {
	fmt.Printf("[myTestPlugin] 用户输入信息:%s\n", firstText(content))
	return nil
}

func (myTestPlugin) BeforeAgent(_ context.Context, _, _, _ string, agent ports.Agent) error {
	fmt.Printf("[myTestPlugin] 智能体名称:%s\n", agent.Name())
	return nil
}

type adkRunnerPlugin struct {
	name   string
	plugin *plugin.Plugin
}

func (p adkRunnerPlugin) Name() string {
	return p.name
}

func (p adkRunnerPlugin) OnUserMessage(_ context.Context, _, _, _ string, _ ports.Agent, content model.ChatContent) error {
	if p.plugin.OnUserMessageCallback() != nil {
		fmt.Printf("[%s] USER MESSAGE RECEIVED %s\n", p.name, firstText(content))
	}
	return nil
}

func (p adkRunnerPlugin) BeforeAgent(_ context.Context, _, _, _ string, agent ports.Agent) error {
	if p.plugin.BeforeAgentCallback() != nil {
		fmt.Printf("[%s] AGENT STARTING %s\n", p.name, agent.Name())
	}
	return nil
}