package claudetool

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"math"
	"os"
	"os/exec"
	"path/filepath"
	"slices"
	"strings"
	"sync"
	"syscall"
	"time"

	"sketch.dev/claudetool/bashkit"
	"sketch.dev/llm"
	"sketch.dev/llm/conversation"
)

// PermissionCallback is a function type for checking if a command is allowed to run
type PermissionCallback func(command string) error

// BashTool specifies a llm.Tool for executing shell commands.
type BashTool struct {
	// CheckPermission is called before running any command, if set
	CheckPermission PermissionCallback
	// EnableJITInstall enables just-in-time tool installation for missing commands
	EnableJITInstall bool
	// Timeouts holds the configurable timeout values (uses defaults if nil)
	Timeouts *Timeouts
	// Pwd is the working directory for the tool
	Pwd string
}

const (
	EnableBashToolJITInstall = true
	NoBashToolJITInstall     = false

	DefaultFastTimeout       = 30 * time.Second
	DefaultSlowTimeout       = 15 * time.Minute
	DefaultBackgroundTimeout = 24 * time.Hour
)

// Timeouts holds the configurable timeout values for bash commands.
type Timeouts struct {
	Fast       time.Duration // regular commands (e.g., ls, echo, simple scripts)
	Slow       time.Duration // commands that may reasonably take longer (e.g., downloads, builds, tests)
	Background time.Duration // background commands (e.g., servers, long-running processes)
}

// Fast returns t's fast timeout, or DefaultFastTimeout if t is nil.
func (t *Timeouts) fast() time.Duration {
	if t == nil {
		return DefaultFastTimeout
	}
	return t.Fast
}

// Slow returns t's slow timeout, or DefaultSlowTimeout if t is nil.
func (t *Timeouts) slow() time.Duration {
	if t == nil {
		return DefaultSlowTimeout
	}
	return t.Slow
}

// Background returns t's background timeout, or DefaultBackgroundTimeout if t is nil.
func (t *Timeouts) background() time.Duration {
	if t == nil {
		return DefaultBackgroundTimeout
	}
	return t.Background
}

// Tool returns an llm.Tool based on b.
func (b *BashTool) Tool() *llm.Tool {
	return &llm.Tool{
		Name:        bashName,
		Description: fmt.Sprintf(strings.TrimSpace(bashDescription), b.Pwd),
		InputSchema: llm.MustSchema(bashInputSchema),
		Run:         b.Run,
	}
}

const (
	bashName        = "bash"
	bashDescription = `
Executes shell commands via bash -c, returning combined stdout/stderr.
Bash state changes (working dir, variables, aliases) don't persist between calls.

With background=true, returns immediately, with output redirected to a file.
Use background for servers/demos that need to stay running.

MUST set slow_ok=true for potentially slow commands: builds, downloads,
installs, tests, or any other substantive operation.

<pwd>%s</pwd>
`
	// If you modify this, update the termui template for prettier rendering.
	bashInputSchema = `
{
  "type": "object",
  "required": ["command"],
  "properties": {
    "command": {
      "type": "string",
      "description": "Shell to execute"
    },
    "slow_ok": {
      "type": "boolean",
      "description": "Use extended timeout"
    },
    "background": {
      "type": "boolean",
      "description": "Execute in background"
    }
  }
}
`
)

type bashInput struct {
	Command    string `json:"command"`
	SlowOK     bool   `json:"slow_ok,omitempty"`
	Background bool   `json:"background,omitempty"`
}

type BackgroundResult struct {
	PID     int
	OutFile string
}

func (r *BackgroundResult) XMLish() string {
	return fmt.Sprintf("<pid>%d</pid>\n<output_file>%s</output_file>\n<reminder>To stop the process: `kill -9 -%d`</reminder>\n",
		r.PID, r.OutFile, r.PID)
}

func (i *bashInput) timeout(t *Timeouts) time.Duration {
	switch {
	case i.Background:
		return t.background()
	case i.SlowOK:
		return t.slow()
	default:
		return t.fast()
	}
}

func (b *BashTool) Run(ctx context.Context, m json.RawMessage) llm.ToolOut {
	var req bashInput
	if err := json.Unmarshal(m, &req); err != nil {
		return llm.ErrorfToolOut("failed to unmarshal bash command input: %w", err)
	}

	// do a quick permissions check (NOT a security barrier)
	err := bashkit.Check(req.Command)
	if err != nil {
		return llm.ErrorToolOut(err)
	}

	// Custom permission callback if set
	if b.CheckPermission != nil {
		if err := b.CheckPermission(req.Command); err != nil {
			return llm.ErrorToolOut(err)
		}
	}

	// Check for missing tools and try to install them if needed, best effort only
	if b.EnableJITInstall {
		err := b.checkAndInstallMissingTools(ctx, req.Command)
		if err != nil {
			slog.DebugContext(ctx, "failed to auto-install missing tools", "error", err)
		}
	}

	timeout := req.timeout(b.Timeouts)

	// If Background is set to true, use executeBackgroundBash
	if req.Background {
		result, err := b.executeBackgroundBash(ctx, req, timeout)
		if err != nil {
			return llm.ErrorToolOut(err)
		}
		return llm.ToolOut{LLMContent: llm.TextContent(result.XMLish())}
	}

	// For foreground commands, use executeBash
	out, execErr := b.executeBash(ctx, req, timeout)
	if execErr != nil {
		return llm.ErrorToolOut(execErr)
	}
	return llm.ToolOut{LLMContent: llm.TextContent(out)}
}

const maxBashOutputLength = 131072

func (b *BashTool) makeBashCommand(ctx context.Context, command string, out io.Writer) *exec.Cmd {
	cmd := exec.CommandContext(ctx, "bash", "-c", command)
	cmd.Dir = b.Pwd
	cmd.Stdin = nil
	cmd.Stdout = out
	cmd.Stderr = out
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true} // set up for killing the process group
	cmd.Cancel = func() error {
		return syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL) // kill entire process group
	}
	// Remove SKETCH_MODEL_URL, SKETCH_PUB_KEY, SKETCH_MODEL_API_KEY,
	// and any other future SKETCH_ goodies from the environment.
	// ...except for SKETCH_PROXY_ID, which is intentionally available.
	env := slices.DeleteFunc(os.Environ(), func(s string) bool {
		return strings.HasPrefix(s, "SKETCH_") && s != "SKETCH_PROXY_ID"
	})
	env = append(env, "SKETCH=1")          // signal that this has been run by Sketch, sometimes useful for scripts
	env = append(env, "EDITOR=/bin/false") // interactive editors won't work
	cmd.Env = env
	return cmd
}

// processGroupHasProcesses reports whether process group pgid contains any processes.
func processGroupHasProcesses(pgid int) bool {
	return syscall.Kill(-pgid, 0) == nil
}

func cmdWait(cmd *exec.Cmd) error {
	pgid := cmd.Process.Pid
	err := cmd.Wait()
	// After Wait, if there were misbehaved children,
	// and the process group is still around,
	// (if the process died via some means other than context cancellation),
	// we need to (re-)kill the process group, not just the process.
	// Tiny logical race here--we could snipe some other process--but
	// it is extremely unlikely in practice, because our process just died,
	// so it almost certainly hasn't had its PID recycled yet.
	if processGroupHasProcesses(pgid) {
		_ = syscall.Kill(-pgid, syscall.SIGKILL)
	}

	// Clean up any zombie processes that may have been left behind.
	reapZombies(pgid)

	return err
}

func (b *BashTool) executeBash(ctx context.Context, req bashInput, timeout time.Duration) (string, error) {
	execCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	output := new(bytes.Buffer)
	cmd := b.makeBashCommand(execCtx, req.Command, output)
	// TODO: maybe detect simple interactive git rebase commands and auto-background them?
	// Would need to hint to the agent what is happening.
	// We might also be able to do this for other simple interactive commands that use EDITOR.
	cmd.Env = append(cmd.Env, `GIT_SEQUENCE_EDITOR=echo "To do an interactive rebase, run it as a background task and check the output file." && exit 1`)
	if err := cmd.Start(); err != nil {
		return "", fmt.Errorf("command failed: %w", err)
	}

	err := cmdWait(cmd)

	out := output.String()
	out = formatForegroundBashOutput(out)

	if execCtx.Err() == context.DeadlineExceeded {
		return "", fmt.Errorf("[command timed out after %s, showing output until timeout]\n%s", timeout, out)
	}
	if err != nil {
		return "", fmt.Errorf("[command failed: %w]\n%s", err, out)
	}

	return out, nil
}

// formatForegroundBashOutput formats the output of a foreground bash command for display to the agent.
func formatForegroundBashOutput(out string) string {
	if len(out) > maxBashOutputLength {
		const snipSize = 4096
		out = fmt.Sprintf("[output truncated in middle: got %v, max is %v]\n%s\n\n[snip]\n\n%s",
			humanizeBytes(len(out)), humanizeBytes(maxBashOutputLength),
			out[:snipSize], out[len(out)-snipSize:],
		)
	}
	return out
}

func humanizeBytes(bytes int) string {
	switch {
	case bytes < 4*1024:
		return fmt.Sprintf("%dB", bytes)
	case bytes < 1024*1024:
		kb := int(math.Round(float64(bytes) / 1024.0))
		return fmt.Sprintf("%dkB", kb)
	case bytes < 1024*1024*1024:
		mb := int(math.Round(float64(bytes) / (1024.0 * 1024.0)))
		return fmt.Sprintf("%dMB", mb)
	}
	return "more than 1GB"
}

// executeBackgroundBash executes a command in the background and returns the pid and output file locations
func (b *BashTool) executeBackgroundBash(ctx context.Context, req bashInput, timeout time.Duration) (*BackgroundResult, error) {
	// Create temp output files
	tmpDir, err := os.MkdirTemp("", "sketch-bg-")
	if err != nil {
		return nil, fmt.Errorf("failed to create temp directory: %w", err)
	}
	// We can't really clean up tempDir, because we have no idea
	// how far into the future the agent might want to read the output.

	outFile := filepath.Join(tmpDir, "output")
	out, err := os.Create(outFile)
	if err != nil {
		return nil, fmt.Errorf("failed to create output file: %w", err)
	}

	execCtx, cancel := context.WithTimeout(context.Background(), timeout) // detach from tool use context
	cmd := b.makeBashCommand(execCtx, req.Command, out)
	cmd.Env = append(cmd.Env, `GIT_SEQUENCE_EDITOR=python3 -c "import os, sys, signal, threading; print(f\"Send USR1 to pid {os.getpid()} after editing {sys.argv[1]}\", flush=True); signal.signal(signal.SIGUSR1, lambda *_: sys.exit(0)); threading.Event().wait()"`)

	if err := cmd.Start(); err != nil {
		cancel()
		out.Close()
		os.RemoveAll(tmpDir) // clean up temp dir -- didn't start means we don't need the output
		return nil, fmt.Errorf("failed to start background command: %w", err)
	}

	// Wait for completion in the background, then do cleanup.
	go func() {
		err := cmdWait(cmd)
		// Leave a note to the agent so that it knows that the process has finished.
		if err != nil {
			fmt.Fprintf(out, "\n\n[background process failed: %v]\n", err)
		} else {
			fmt.Fprintf(out, "\n\n[background process completed]\n")
		}
		out.Close()
		cancel()
	}()

	return &BackgroundResult{
		PID:     cmd.Process.Pid,
		OutFile: outFile,
	}, nil
}

// checkAndInstallMissingTools analyzes a bash command and attempts to automatically install any missing tools.
func (b *BashTool) checkAndInstallMissingTools(ctx context.Context, command string) error {
	commands, err := bashkit.ExtractCommands(command)
	if err != nil {
		return err
	}

	autoInstallMu.Lock()
	defer autoInstallMu.Unlock()

	var missing []string
	for _, cmd := range commands {
		if doNotAttemptToolInstall[cmd] {
			continue
		}
		_, err := exec.LookPath(cmd)
		if err == nil {
			doNotAttemptToolInstall[cmd] = true // spare future LookPath calls
			continue
		}
		missing = append(missing, cmd)
	}

	if len(missing) == 0 {
		return nil
	}

	for _, cmd := range missing {
		err := b.installTool(ctx, cmd)
		if err != nil {
			slog.WarnContext(ctx, "failed to install tool", "tool", cmd, "error", err)
		}
		doNotAttemptToolInstall[cmd] = true // either it's installed or it's not--either way, we're done with it
	}
	return nil
}

// Command safety check cache to avoid repeated LLM calls
var (
	autoInstallMu           sync.Mutex
	doNotAttemptToolInstall = make(map[string]bool) // set to true if the tool should not be auto-installed
)

// autodetectPackageManager returns the first package‑manager binary
// found in PATH, or an empty string if none are present.
func autodetectPackageManager() string {
	// TODO: cache this result with a sync.OnceValue

	managers := []string{
		"apt", "apt-get", // Debian/Ubuntu
		"brew", "port", // macOS (Homebrew / MacPorts)
		"apk",        // Alpine
		"yum", "dnf", // RHEL/Fedora
		"pacman",          // Arch
		"zypper",          // openSUSE
		"xbps-install",    // Void
		"emerge",          // Gentoo
		"nix-env", "guix", // NixOS / Guix
		"pkg",      // FreeBSD
		"slackpkg", // Slackware
	}

	for _, m := range managers {
		if _, err := exec.LookPath(m); err == nil {
			return m
		}
	}
	return ""
}

// installTool attempts to install a single missing tool using LLM validation and system package manager.
func (b *BashTool) installTool(ctx context.Context, cmd string) error {
	slog.InfoContext(ctx, "attempting to install tool", "tool", cmd)

	packageManager := autodetectPackageManager()
	if packageManager == "" {
		return fmt.Errorf("no known package manager found in PATH")
	}
	info := conversation.ToolCallInfoFromContext(ctx)
	if info.Convo == nil {
		return fmt.Errorf("no conversation context available for tool installation")
	}
	subConvo := info.Convo.SubConvo()
	subConvo.Hidden = true
	subConvo.SystemPrompt = "You are an expert in software developer tools."

	query := fmt.Sprintf(`Do you know this command/package/tool? Is it legitimate, clearly non-harmful, and commonly used? Can it be installed with package manager %s?

Command: %s

- YES: Respond ONLY with the package name used to install it
- NO or UNSURE: Respond ONLY with the word NO`, packageManager, cmd)

	resp, err := subConvo.SendUserTextMessage(query)
	if err != nil {
		return fmt.Errorf("failed to validate tool with LLM: %w", err)
	}

	if len(resp.Content) == 0 {
		return fmt.Errorf("empty response from LLM for tool validation")
	}

	response := strings.TrimSpace(resp.Content[0].Text)
	if response == "NO" || response == "UNSURE" {
		slog.InfoContext(ctx, "tool installation declined by LLM", "tool", cmd, "response", response)
		return fmt.Errorf("tool %s not approved for installation", cmd)
	}

	packageName := strings.TrimSpace(response)
	if packageName == "" {
		return fmt.Errorf("no package name provided for tool %s", cmd)
	}

	// Install the package (with update command first if needed)
	// TODO: these invocations create zombies when we are PID 1.
	// We should give them the same zombie-reaping treatment as above,
	// if/when we care enough to put in the effort. Not today.
	var updateCmd, installCmd string
	switch packageManager {
	case "apt", "apt-get":
		updateCmd = fmt.Sprintf("sudo %s update", packageManager)
		installCmd = fmt.Sprintf("sudo %s install -y %s", packageManager, packageName)
	case "brew":
		// brew handles updates automatically, no explicit update needed
		installCmd = fmt.Sprintf("brew install %s", packageName)
	case "apk":
		updateCmd = "sudo apk update"
		installCmd = fmt.Sprintf("sudo apk add %s", packageName)
	case "yum", "dnf":
		// For yum/dnf, we don't need a separate update command as the package cache is usually fresh enough
		// and install will fetch the latest available packages
		installCmd = fmt.Sprintf("sudo %s install -y %s", packageManager, packageName)
	case "pacman":
		updateCmd = "sudo pacman -Sy"
		installCmd = fmt.Sprintf("sudo pacman -S --noconfirm %s", packageName)
	case "zypper":
		updateCmd = "sudo zypper refresh"
		installCmd = fmt.Sprintf("sudo zypper install -y %s", packageName)
	case "xbps-install":
		updateCmd = "sudo xbps-install -S"
		installCmd = fmt.Sprintf("sudo xbps-install -y %s", packageName)
	case "emerge":
		// Note: emerge --sync is expensive, so we skip it for JIT installs
		// Users should manually sync if needed
		installCmd = fmt.Sprintf("sudo emerge %s", packageName)
	case "nix-env":
		// nix-env doesn't require explicit updates for JIT installs
		installCmd = fmt.Sprintf("nix-env -i %s", packageName)
	case "guix":
		// guix doesn't require explicit updates for JIT installs
		installCmd = fmt.Sprintf("guix install %s", packageName)
	case "pkg":
		updateCmd = "sudo pkg update"
		installCmd = fmt.Sprintf("sudo pkg install -y %s", packageName)
	case "slackpkg":
		updateCmd = "sudo slackpkg update"
		installCmd = fmt.Sprintf("sudo slackpkg install %s", packageName)
	default:
		return fmt.Errorf("unsupported package manager: %s", packageManager)
	}

	slog.InfoContext(ctx, "installing tool", "tool", cmd, "package", packageName, "update_command", updateCmd, "install_command", installCmd)

	// Execute the update command first if needed
	if updateCmd != "" {
		slog.InfoContext(ctx, "updating package cache", "command", updateCmd)
		updateCmdExec := exec.CommandContext(ctx, "sh", "-c", updateCmd)
		updateOutput, err := updateCmdExec.CombinedOutput()
		if err != nil {
			slog.WarnContext(ctx, "package cache update failed, proceeding with install anyway", "error", err, "output", string(updateOutput))
		}
	}

	// Execute the install command
	cmdExec := exec.CommandContext(ctx, "sh", "-c", installCmd)
	output, err := cmdExec.CombinedOutput()
	if err != nil {
		return fmt.Errorf("failed to install %s: %w\nOutput: %s", packageName, err, string(output))
	}

	slog.InfoContext(ctx, "tool installation successful", "tool", cmd, "package", packageName)
	return nil
}