package agent

import (
	"context"
	"os"
	"path/filepath"
	"strings"

	"chat-agent-system/internal/agentx"
	"chat-agent-system/internal/agentx/llm"
	"chat-agent-system/internal/agentx/session"
	"chat-agent-system/internal/agentx/tools"
	"chat-agent-system/internal/config"
	"chat-agent-system/internal/workspace"
)

// PiNativeBackend runs the in-process Go agent loop. The container pi-agent backend stays available.
type PiNativeBackend struct {
	cfg    *config.Config
	stream llm.StreamFunc
}

func NewPiNativeBackend(cfg *config.Config) *PiNativeBackend {
	return &PiNativeBackend{cfg: cfg}
}

func (p *PiNativeBackend) Name() string { return "pi-native" }

func (p *PiNativeBackend) Execute(ctx context.Context, req Request) (*Result, error) {
	if len(req.Targets) == 0 {
		req.Targets = []string{workspace.DeliverableKey}
	}
	profile := strings.TrimSpace(req.ToolProfile)
	if profile == "" {
		profile = ToolProfileWorkspace
	}
	if profile != ToolProfileWorkspace && profile != ToolProfileReasoning {
		return &Result{Success: false, ErrorReason: "unknown tool profile"}, nil
	}
	if p.stream == nil && (p.cfg == nil || strings.TrimSpace(p.cfg.AgentXAPIKey) == "") {
		return &Result{Success: false, ErrorReason: "agentx api key is not configured"}, nil
	}

	workDir := req.WorkDir
	if !filepath.IsAbs(workDir) {
		wd, _ := os.Getwd()
		workDir = filepath.Join(wd, workDir)
	}
	if err := os.MkdirAll(workDir, 0o755); err != nil {
		return &Result{Success: false, ErrorReason: err.Error()}, nil
	}
	if p.cfg != nil {
		_ = workspace.NoteWorkspace(p.cfg.DataDir, workDir, filepath.Base(workDir))
	}
	if strings.TrimSpace(req.Instructions) != "" {
		_ = os.WriteFile(filepath.Join(workDir, "INSTRUCTIONS.md"), []byte(req.Instructions), 0o644)
		_ = os.WriteFile(filepath.Join(workDir, "AGENTS.md"), []byte(req.Instructions), 0o644)
	}
	if strings.TrimSpace(req.Prompt) != "" {
		_ = os.WriteFile(filepath.Join(workDir, "TASK.md"), []byte(req.Prompt), 0o644)
	}

	var reg *tools.Registry
	if profile == ToolProfileWorkspace {
		reg = tools.WorkspaceTools(workDir)
	}
	store, err := session.Open(filepath.Join(workDir, ".agentx", "transcript.jsonl"))
	if err != nil {
		return &Result{Success: false, ErrorReason: err.Error()}, nil
	}
	stream := p.stream
	model := "MiniMax-M2.7-highspeed"
	if p.cfg != nil && p.cfg.AgentXModel != "" {
		model = p.cfg.AgentXModel
	}
	if stream == nil {
		client := &llm.Client{BaseURL: p.cfg.AgentXAPIBase, APIKey: p.cfg.AgentXAPIKey}
		stream = client.Stream
	}

	timeout := req.Timeout
	if timeout <= 0 && p.cfg != nil {
		timeout = p.cfg.AgentXTimeout
	}
	if timeout <= 0 && p.cfg != nil {
		timeout = p.cfg.AgentTimeout
	}
	runCtx := ctx
	cancel := func() {}
	if timeout > 0 {
		runCtx, cancel = context.WithTimeout(ctx, timeout)
	}
	defer cancel()

	var logs strings.Builder
	onProcess := req.OnEvent
	runRes, err := agentx.Run(runCtx, agentx.Config{
		Model:        model,
		SystemPrompt: nativeSystemPrompt(req, profile),
		Tools:        reg,
		Stream:       stream,
		Session:      store,
		OnEvent: func(ev agentx.Event) {
			logs.WriteString(ev.Type)
			if ev.Tool != "" {
				logs.WriteString(" ")
				logs.WriteString(ev.Tool)
			}
			if ev.Text != "" {
				logs.WriteString(" ")
				logs.WriteString(ev.Text)
			}
			logs.WriteByte('\n')
			if onProcess != nil {
				onProcess(ProcessEvent{
					Type:   ev.Type,
					Text:   ev.Text,
					Tool:   ev.Tool,
					Detail: ev.Detail,
				})
			}
		},
	}, llm.Message{Role: llm.RoleUser, Content: req.Prompt})
	if err != nil {
		return &Result{Success: false, ErrorReason: err.Error(), Logs: logs.String()}, nil
	}
	_ = os.WriteFile(filepath.Join(workDir, "execution.log"), []byte(logs.String()), 0o644)

	if profile == ToolProfileReasoning && strings.TrimSpace(runRes.Text) != "" {
		for _, target := range req.Targets {
			path := filepath.Join(workDir, filepath.FromSlash(target))
			if b, err := os.ReadFile(path); err == nil && len(strings.TrimSpace(string(b))) > 0 {
				continue
			}
			_ = os.MkdirAll(filepath.Dir(path), 0o755)
			_ = os.WriteFile(path, []byte(runRes.Text), 0o644)
		}
	}

	if runRes.Err != nil {
		reason := runRes.Err.Error()
		res := &Result{Success: false, ErrorReason: reason, Logs: logs.String(), Retryable: runRes.Retryable}
		if runRes.StopReason == llm.StopAborted {
			res.Retryable = true
		}
		return res, nil
	}

	patches, matErr := MaterializeTargets(workDir, req.Targets, nil)
	if matErr != nil {
		return &Result{Success: false, ErrorReason: matErr.Error(), Patches: patches, Logs: logs.String()}, nil
	}
	return &Result{
		Success:          true,
		Patches:          patches,
		Logs:             logs.String(),
		PromptTokens:     runRes.Usage.PromptTokens,
		CompletionTokens: runRes.Usage.CompletionTokens,
	}, nil
}

func nativeSystemPrompt(req Request, profile string) string {
	var b strings.Builder
	if strings.TrimSpace(req.Instructions) != "" {
		b.WriteString(req.Instructions)
		b.WriteString("\n\n")
	}
	b.WriteString("Deliverable files: ")
	b.WriteString(strings.Join(req.Targets, ", "))
	b.WriteString(".")
	if profile == ToolProfileWorkspace {
		b.WriteString(" Use workspace tools to write those files. Do not invent paths outside the workspace.")
	} else {
		b.WriteString(" Reply with the deliverable text only. Tools are disabled.")
	}
	return b.String()
}