package executor

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

	"github.com/thepeterstone/claudomator/internal/storage"
	"github.com/thepeterstone/claudomator/internal/task"
)

// GeminiRunner spawns the `gemini` CLI in non-interactive mode.
type GeminiRunner struct {
	BinaryPath string // defaults to "gemini"
	Logger     *slog.Logger
	LogDir     string // base directory for execution logs
	APIURL     string // base URL of the Claudomator API, passed to subprocesses
}

// ExecLogDir returns the log directory for the given execution ID.
func (r *GeminiRunner) ExecLogDir(execID string) string {
	if r.LogDir == "" {
		return ""
	}
	return filepath.Join(r.LogDir, execID)
}

func (r *GeminiRunner) binaryPath() string {
	if r.BinaryPath != "" {
		return r.BinaryPath
	}
	return "gemini"
}

// Run executes the gemini CLI inside a sandboxed clone of project_dir.
// When project_dir is set, claudomator first clones it into a temp sandbox
// (preferring a `local` bare remote, then `origin`, then the working tree)
// and runs the agent there. On success the sandbox is autocommitted and
// pushed back to origin/master, then removed. On failure the sandbox is
// preserved and its path is included in the returned error so the user can
// inspect partial work. If the agent writes a question file before exiting,
// Run returns *BlockedError with SandboxDir populated so a resume execution
// can pick up in the same directory.
func (r *GeminiRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
	projectDir := t.Agent.ProjectDir

	if projectDir != "" {
		if _, err := os.Stat(projectDir); err != nil {
			return fmt.Errorf("project_dir %q: %w", projectDir, err)
		}
	}

	logDir := r.ExecLogDir(e.ID)
	if logDir == "" {
		logDir = e.ID
	}
	if err := os.MkdirAll(logDir, 0700); err != nil {
		return fmt.Errorf("creating log dir: %w", err)
	}

	if e.StdoutPath == "" {
		e.StdoutPath = filepath.Join(logDir, "stdout.log")
		e.StderrPath = filepath.Join(logDir, "stderr.log")
		e.ArtifactDir = logDir
	}

	if e.SessionID == "" {
		if e.ResumeSessionID != "" {
			e.SessionID = e.ResumeSessionID
		} else {
			e.SessionID = e.ID
		}
	}

	// Sandbox setup: for new executions with a project_dir, clone into a sandbox.
	// Resume executions reuse the preserved sandbox so any partial work survives.
	// If the preserved sandbox is missing (e.g. /tmp was purged), clone fresh.
	var sandboxDir string
	var startHEAD string
	effectiveWorkingDir := projectDir
	if e.ResumeSessionID != "" {
		if e.SandboxDir != "" {
			if _, statErr := os.Stat(e.SandboxDir); statErr == nil {
				effectiveWorkingDir = e.SandboxDir
			} else {
				r.Logger.Warn("preserved sandbox missing, cloning fresh", "sandbox", e.SandboxDir, "project_dir", projectDir)
				e.SandboxDir = ""
				if projectDir != "" {
					var err error
					sandboxDir, err = setupSandbox(projectDir, r.Logger)
					if err != nil {
						return fmt.Errorf("setting up sandbox: %w", err)
					}
					effectiveWorkingDir = sandboxDir
					r.Logger.Info("fresh sandbox created for resume", "sandbox", sandboxDir, "project_dir", projectDir)
				}
			}
		}
	} else if projectDir != "" {
		var err error
		sandboxDir, err = setupSandbox(projectDir, r.Logger)
		if err != nil {
			return fmt.Errorf("setting up sandbox: %w", err)
		}
		effectiveWorkingDir = sandboxDir
		r.Logger.Info("sandbox created", "sandbox", sandboxDir, "project_dir", projectDir)
	}

	if effectiveWorkingDir != "" {
		headOut, _ := exec.Command("git", gitSafe("-C", effectiveWorkingDir, "rev-parse", "HEAD")...).Output()
		startHEAD = strings.TrimSpace(string(headOut))
	}

	questionFile := filepath.Join(logDir, "question.json")
	args := r.buildArgs(t, e, questionFile)

	if err := r.execOnce(ctx, args, effectiveWorkingDir, projectDir, e); err != nil {
		if sandboxDir != "" {
			return fmt.Errorf("%w (sandbox preserved at %s)", err, sandboxDir)
		}
		return err
	}

	// Check whether the agent left a question before exiting.
	data, readErr := os.ReadFile(questionFile)
	if readErr == nil {
		os.Remove(questionFile)
		questionJSON := strings.TrimSpace(string(data))
		if isCompletionReport(questionJSON) {
			r.Logger.Info("treating question file as completion report", "taskID", e.TaskID)
			e.Summary = extractQuestionText(questionJSON)
		} else {
			// Preserve sandbox on BLOCKED so a resume can pick up in the same dir.
			return &BlockedError{QuestionJSON: questionJSON, SessionID: e.SessionID, SandboxDir: sandboxDir}
		}
	}

	// Read agent summary if written.
	summaryFile := filepath.Join(logDir, "summary.txt")
	if summaryData, readErr := os.ReadFile(summaryFile); readErr == nil {
		os.Remove(summaryFile)
		e.Summary = strings.TrimSpace(string(summaryData))
	}

	// Merge sandbox back to project_dir and clean up.
	if sandboxDir != "" {
		if mergeErr := teardownSandbox(projectDir, sandboxDir, startHEAD, r.Logger, e); mergeErr != nil {
			return fmt.Errorf("sandbox teardown: %w (sandbox preserved at %s)", mergeErr, sandboxDir)
		}
	}
	return nil
}

func (r *GeminiRunner) execOnce(ctx context.Context, args []string, workingDir, projectDir string, e *storage.Execution) error {
	cmd := exec.CommandContext(ctx, r.binaryPath(), args...)
	cmd.Env = append(os.Environ(),
		"CLAUDOMATOR_API_URL="+r.APIURL,
		"CLAUDOMATOR_TASK_ID="+e.TaskID,
		"CLAUDOMATOR_PROJECT_DIR="+projectDir,
		"CLAUDOMATOR_QUESTION_FILE="+filepath.Join(e.ArtifactDir, "question.json"),
		"CLAUDOMATOR_SUMMARY_FILE="+filepath.Join(e.ArtifactDir, "summary.txt"),
	)
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
	if workingDir != "" {
		cmd.Dir = workingDir
	}

	stdoutFile, err := os.Create(e.StdoutPath)
	if err != nil {
		return fmt.Errorf("creating stdout log: %w", err)
	}
	defer stdoutFile.Close()

	stderrFile, err := os.Create(e.StderrPath)
	if err != nil {
		return fmt.Errorf("creating stderr log: %w", err)
	}
	defer stderrFile.Close()

	stdoutR, stdoutW, err := os.Pipe()
	if err != nil {
		return fmt.Errorf("creating stdout pipe: %w", err)
	}
	cmd.Stdout = stdoutW
	cmd.Stderr = stderrFile

	if err := cmd.Start(); err != nil {
		stdoutW.Close()
		stdoutR.Close()
		return fmt.Errorf("starting gemini: %w", err)
	}
	stdoutW.Close()

	killDone := make(chan struct{})
	go func() {
		select {
		case <-ctx.Done():
			syscall.Kill(-cmd.Process.Pid, syscall.SIGKILL)
		case <-killDone:
		}
	}()

	var streamCost float64
	var streamErr error
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		streamCost, streamErr = parseGeminiStream(stdoutR, stdoutFile, r.Logger)
		stdoutR.Close()
	}()

	waitErr := cmd.Wait()
	close(killDone)
	wg.Wait()

	if streamCost > 0 {
		e.CostUSD = streamCost
	}

	if waitErr != nil {
		if exitErr, ok := waitErr.(*exec.ExitError); ok {
			e.ExitCode = exitErr.ExitCode()
		}
		if streamErr != nil {
			return streamErr
		}
		if tail := tailFile(e.StderrPath, 20); tail != "" {
			return fmt.Errorf("gemini exited with error: %w\nstderr:\n%s", waitErr, tail)
		}
		return fmt.Errorf("gemini exited with error: %w", waitErr)
	}

	if streamErr != nil {
		return streamErr
	}
	return nil
}

// parseGeminiStream reads streaming JSON from the gemini CLI, strips markdown
// code fences if the output is wrapped in them, writes the inner stream-json
// to w, and returns (costUSD, error). If a `result` event has `is_error: true`,
// an error wrapping the result message is returned.
func parseGeminiStream(r io.Reader, w io.Writer, logger *slog.Logger) (float64, error) {
	fullOutput, err := io.ReadAll(r)
	if err != nil {
		return 0, fmt.Errorf("reading full gemini output: %w", err)
	}
	logger.Debug("parseGeminiStream: raw output received", "output", string(fullOutput))

	inner := stripGeminiFences(string(fullOutput), logger)
	if _, writeErr := w.Write([]byte(inner)); writeErr != nil {
		return 0, fmt.Errorf("writing gemini output: %w", writeErr)
	}

	// Walk lines looking for a result event so we can surface errors and cost.
	var (
		cost    float64
		errMsg  string
		isError bool
	)
	for _, raw := range strings.Split(inner, "\n") {
		line := strings.TrimSpace(raw)
		if line == "" {
			continue
		}
		var evt struct {
			Type    string  `json:"type"`
			IsError bool    `json:"is_error"`
			Result  string  `json:"result"`
			Cost    float64 `json:"total_cost_usd"`
		}
		if err := json.Unmarshal([]byte(line), &evt); err != nil {
			continue
		}
		if evt.Type == "result" {
			if evt.Cost > 0 {
				cost = evt.Cost
			}
			if evt.IsError {
				isError = true
				errMsg = evt.Result
			}
		}
	}
	if isError {
		return cost, fmt.Errorf("gemini reported error: %s", errMsg)
	}
	return cost, nil
}

// stripGeminiFences removes a surrounding ```json ... ``` markdown block if
// present, returning the trimmed inner content. If no markdown fence is
// found, the input is returned verbatim (no whitespace trimming) so callers
// that expect byte-exact pass-through behavior get it.
func stripGeminiFences(raw string, logger *slog.Logger) string {
	trimmed := strings.TrimSpace(raw)
	if start := strings.Index(trimmed, "```json"); start != -1 {
		if end := strings.LastIndex(trimmed, "```"); end > start {
			return strings.TrimSpace(trimmed[start+len("```json") : end])
		}
		logger.Warn("malformed gemini markdown block (missing closing fence); using raw output", "len", len(trimmed))
		return trimmed
	}
	return raw
}

func (r *GeminiRunner) buildArgs(t *task.Task, e *storage.Execution, questionFile string) []string {
	// Gemini CLI uses a different command structure: gemini "instructions" [flags]
	
	instructions := t.Agent.Instructions
	if !t.Agent.SkipPlanning {
		instructions = withPlanningPreamble(instructions)
	}

	args := []string{
		"-p", instructions,
		"--output-format", "stream-json",
		"--yolo", // auto-approve all tools (equivalent to Claude's bypassPermissions)
	}

	// Note: Gemini CLI flags might differ from Claude CLI.
	// Assuming common flags for now, but these may need adjustment.
	if t.Agent.Model != "" {
		args = append(args, "--model", t.Agent.Model)
	}
	
	// Gemini CLI doesn't use --session-id for the first run in the same way,
	// or it might use it differently. For now we assume compatibility.
	if e.SessionID != "" {
		// If it's a resume, it might use different flags.
		if e.ResumeSessionID != "" {
			// This is a placeholder for Gemini's resume logic
		}
	}

	return args
}