// Package exec handles tool execution in sandboxed environments.
package exec

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"os"
	osExec "os/exec"
	"path/filepath"
	"strings"
	"syscall"
	"time"

	"ollie/cmd/toolsrv/internal/bypass"
	"ollie/cmd/toolsrv/internal/sandbox"
	"ollie/toolsrv/metadata"
	"ollie/toolsrv/protocol"
	"ollie/util"
)

// StartResult reports whether an external command started.
type StartResult struct {
	Process *os.Process
	Err     error
}

// Config contains all context needed for tool execution.
type Config struct {
	CWD     string
	Env     map[string]string
	Yolo    bool
	Timeout int              // 0 = no timeout
	Output  io.Writer        // if set, stream stdout/stderr here in real-time
	Started chan StartResult // receives exactly one startup result if set
}

// StreamFunc returns the streaming output function from context, if any.
func StreamFunc(ctx context.Context) func(string) {
	if fn, ok := ctx.Value(streamKey{}).(func(string)); ok {
		return fn
	}
	return nil
}

type streamKey struct{}

// WithStreamFunc attaches a streaming output function to context.
func WithStreamFunc(ctx context.Context, fn func(string)) context.Context {
	return context.WithValue(ctx, streamKey{}, fn)
}

// ExecuteTool runs a tool script with the given args and returns the result.
func ExecuteTool(ctx context.Context, info protocol.ToolInfo, args json.RawMessage, cfg Config) (json.RawMessage, error) {
	// Resolve script path
	toolPath, err := metadata.ResolveTool(info.Name)
	if err != nil {
		return nil, fmt.Errorf("resolve tool %s: %w", info.Name, err)
	}

	// Extract dispatch-level flags from args
	bypassed := false
	timeout := cfg.Timeout // 0 = no timeout; caller sets default

	var argMap map[string]interface{}
	if err := json.Unmarshal(args, &argMap); err == nil {
		if e, ok := argMap["bypass"]; ok {
			switch v := e.(type) {
			case bool:
				bypassed = v
			case string:
				bypassed = v == "true" || v == "1"
			}
			delete(argMap, "bypass")
		}
		if t, ok := argMap["timeout"]; ok {
			switch v := t.(type) {
			case float64:
				timeout = int(v)
			case string:
				var n int
				if _, err := fmt.Sscanf(v, "%d", &n); err == nil {
					timeout = n
				}
			}
			delete(argMap, "timeout")
		}
		delete(argMap, "sandbox") // ignored, single config
		args, _ = json.Marshal(argMap)
	}

	stdinData := string(args)
	cwd := cfg.CWD
	if cwd == "" {
		cwd, _ = os.Getwd()
	}

	var result string
	if bypassed {
		bypassCode := fmt.Sprintf("cat <<'OLLIE_EOF' | %s\n%s\nOLLIE_EOF", toolPath, stdinData)
		result, err = executeBypassDirect(ctx, bypassCode, cwd, cfg.Env, timeout, cfg.Started)
	} else {
		result, err = executeSandboxed(ctx, toolPath, stdinData, cwd, cfg.Env, timeout, cfg.Yolo, cfg.Output, cfg.Started)
	}

	if err != nil {
		return json.Marshal(protocol.ToolResult{
			IsError: true,
			Content: []protocol.ToolResultContent{{Type: "text", Text: result + ": " + err.Error()}},
		})
	}
	return json.Marshal(protocol.ToolResult{
		Content: []protocol.ToolResultContent{{Type: "text", Text: result}},
	})
}

// executeSandboxed runs a tool script inside the sandbox.
func executeSandboxed(ctx context.Context, toolPath, stdinData, cwd string, envExtra map[string]string, timeout int, yolo bool, streamOut io.Writer, started chan StartResult) (string, error) {
	startedSent := false
	defer func() {
		if started != nil && !startedSent {
			started <- StartResult{Err: fmt.Errorf("execution did not start")}
		}
	}()

	var sandboxCfg *sandbox.Config
	if !yolo {
		cfgPath := filepath.Join(util.CfgDir(), "sandbox.yaml")
		f, err := os.Open(cfgPath)
		if err != nil {
			return "", fmt.Errorf("sandbox config not found: %w", err)
		}
		defer f.Close()
		var loadErr error
		sandboxCfg, loadErr = sandbox.LoadSandbox(f)
		if loadErr != nil {
			return "", loadErr
		}
	}

	if timeout > 0 {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, time.Duration(timeout)*time.Second)
		defer cancel()
	}

	interpreter := []string{"bash", "-c", toolPath}

	// Build environment
	envMap := make(map[string]string)
	for _, ev := range os.Environ() {
		k, v, _ := strings.Cut(ev, "=")
		envMap[k] = v
	}
	for k, v := range envExtra {
		envMap[k] = v
	}
	// Prepend tools directory to PATH so meta-only cmd fields can reference other tools
	if toolsDir := metadata.ToolsPath(); toolsDir != "" {
		if existing := envMap["PATH"]; existing != "" {
			envMap["PATH"] = toolsDir + ":" + existing
		} else {
			envMap["PATH"] = toolsDir
		}
	}
	// Compute NAMESPACE if not set
	if _, ok := envMap["NAMESPACE"]; !ok {
		if ns := Plan9Namespace(envMap); ns != "" {
			envMap["NAMESPACE"] = ns
		}
	}

	var cmd *osExec.Cmd
	if yolo {
		cmd = osExec.CommandContext(ctx, interpreter[0], interpreter[1:]...)
	} else {
		wrapped, wrapErr := sandbox.NativeCommand(sandboxCfg, interpreter, cwd, envMap)
		if wrapErr != nil {
			return "", wrapErr
		}
		cmd = osExec.CommandContext(ctx, wrapped[0], wrapped[1:]...)
	}

	cmd.Dir = cwd
	if stdinData != "" {
		cmd.Stdin = strings.NewReader(stdinData)
	}

	// Set environment
	for k, v := range envMap {
		cmd.Env = append(cmd.Env, k+"="+v)
	}

	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true, Pdeathsig: syscall.SIGKILL}
	cmd.Cancel = func() error {
		if cmd.Process != nil {
			syscall.Kill(-cmd.Process.Pid, syscall.SIGTERM)
		}
		return nil
	}
	cmd.WaitDelay = 5 * time.Second

	var outputBuf bytes.Buffer
	var w io.Writer = &outputBuf
	if streamOut != nil {
		w = io.MultiWriter(&outputBuf, streamOut)
	}
	lw := &limitedWriter{
		w:      w,
		limit:  10 * 1024 * 1024,
		stream: StreamFunc(ctx),
	}
	cmd.Stdout = lw
	cmd.Stderr = lw

	if err := cmd.Start(); err != nil {
		if started != nil {
			started <- StartResult{Err: fmt.Errorf("execution failed: %w", err)}
			startedSent = true
		}
		return "", fmt.Errorf("execution failed: %w", err)
	}

	if started != nil {
		started <- StartResult{Process: cmd.Process}
		startedSent = true
	}

	err := cmd.Wait()
	output := outputBuf.Bytes()
	if lw.truncated {
		output = append(output, []byte("\n[output truncated at 10MB]")...)
	}

	if ctx.Err() == context.DeadlineExceeded {
		return string(output), fmt.Errorf("execution timeout after %d seconds", timeout)
	}
	if err != nil {
		errOutput := string(output)
		const maxErrOutput = 8192
		if len(errOutput) > maxErrOutput {
			errOutput = errOutput[:maxErrOutput] + fmt.Sprintf("\n[...truncated %d bytes in error]", len(output)-maxErrOutput)
		}
		return string(output), fmt.Errorf("execution failed: %w\nOutput: %s", err, errOutput)
	}
	return string(output), nil
}

// executeBypassDirect requests bypass approval and executes the command directly.
// The approval comes from olliesrv via the 9P bypass/pending and bypass/resolve files.
func executeBypassDirect(ctx context.Context, cmd, cwd string, envExtra map[string]string, timeout int, started chan StartResult) (string, error) {
	// Build environment map
	envMap := make(map[string]string)
	for _, kv := range os.Environ() {
		if k, v, ok := strings.Cut(kv, "="); ok {
			envMap[k] = v
		}
	}
	for k, v := range envExtra {
		envMap[k] = v
	}

	// Submit bypass request and wait for approval
	approved, err := bypass.Submit(ctx, cmd, cwd, envMap)
	if err != nil {
		if started != nil {
			started <- StartResult{Err: fmt.Errorf("bypass request failed: %w", err)}
		}
		return "", fmt.Errorf("bypass request failed: %w", err)
	}
	if !approved {
		if started != nil {
			started <- StartResult{Err: fmt.Errorf("bypass denied")}
		}
		return "", fmt.Errorf("bypass denied")
	}

	// Approved - execute directly without sandbox
	if timeout > 0 {
		var cancel context.CancelFunc
		ctx, cancel = context.WithTimeout(ctx, time.Duration(timeout)*time.Second)
		defer cancel()
	}

	return executeDirectUnsandboxed(ctx, cmd, cwd, envMap, started)
}

// executeDirectUnsandboxed runs a command without any sandbox.
func executeDirectUnsandboxed(ctx context.Context, cmd, cwd string, env map[string]string, started chan StartResult) (string, error) {
	execCmd := osExec.CommandContext(ctx, "bash", "-c", cmd)
	execCmd.Dir = cwd
	if len(env) > 0 {
		execCmd.Env = make([]string, 0, len(env))
		for k, v := range env {
			execCmd.Env = append(execCmd.Env, k+"="+v)
		}
	}

	var stdout, stderr bytes.Buffer
	execCmd.Stdout = &stdout
	execCmd.Stderr = &stderr

	// Stream output if context has a stream function
	if stream := StreamFunc(ctx); stream != nil {
		execCmd.Stdout = io.MultiWriter(&stdout, &streamWriter{stream})
		execCmd.Stderr = io.MultiWriter(&stderr, &streamWriter{stream})
	}

	if err := execCmd.Start(); err != nil {
		if started != nil {
			started <- StartResult{Err: fmt.Errorf("bypass execution failed: %w", err)}
		}
		return "", err
	}
	if started != nil {
		started <- StartResult{Process: execCmd.Process}
	}
	err := execCmd.Wait()
	output := stdout.String()
	if stderr.Len() > 0 {
		if output != "" {
			output += "\n"
		}
		output += stderr.String()
	}

	if err != nil {
		if exitErr, ok := err.(*osExec.ExitError); ok {
			return output, fmt.Errorf("exit %d", exitErr.ExitCode())
		}
		return output, err
	}
	return output, nil
}

// streamWriter adapts a stream function to io.Writer.
type streamWriter struct {
	fn func(string)
}

func (w *streamWriter) Write(p []byte) (int, error) {
	w.fn(string(p))
	return len(p), nil
}

// Plan9Namespace computes the Plan 9 namespace directory.
func Plan9Namespace(env map[string]string) string {
	if ns := env["NAMESPACE"]; ns != "" {
		return ns
	}
	disp := env["DISPLAY"]
	if disp == "" {
		return "/tmp/ns." + env["USER"] + "." + "unix"
	}
	// Strip leading "localhost" if present
	disp = strings.TrimPrefix(disp, "localhost")
	disp = strings.ReplaceAll(disp, "/", "_")
	return "/tmp/ns." + env["USER"] + "." + disp
}

// limitedWriter wraps a writer with a size limit and optional streaming.
type limitedWriter struct {
	w         io.Writer
	limit     int
	written   int
	truncated bool
	stream    func(string)
}

func (lw *limitedWriter) Write(p []byte) (int, error) {
	if lw.truncated {
		return len(p), nil // discard but report success
	}
	remaining := lw.limit - lw.written
	if remaining <= 0 {
		lw.truncated = true
		return len(p), nil
	}
	toWrite := p
	if len(p) > remaining {
		toWrite = p[:remaining]
		lw.truncated = true
	}
	n, err := lw.w.Write(toWrite)
	lw.written += n
	if lw.stream != nil && n > 0 {
		lw.stream(string(toWrite[:n]))
	}
	return len(p), err
}