package executor

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

	"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
	DropsDir   string // path to the drops directory, 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 a gemini <instructions> invocation, streaming output to log files.
func (r *GeminiRunner) Run(ctx context.Context, t *task.Task, e *storage.Execution) error {
	if t.Agent.ProjectDir != "" {
		if _, err := os.Stat(t.Agent.ProjectDir); err != nil {
			return fmt.Errorf("project_dir %q: %w", t.Agent.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 == "" {
		e.SessionID = e.ID
	}

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

	// Gemini CLI doesn't necessarily have the same rate limiting behavior as Claude,
	// but we'll use a similar execution pattern.
	err := r.execOnce(ctx, args, t.Agent.ProjectDir, t.Agent.ProjectDir, e)
	if err != nil {
		return err
	}

	// Check whether the agent left a question before exiting.
	data, readErr := os.ReadFile(questionFile)
	if readErr == nil {
		os.Remove(questionFile) // consumed
		return &BlockedError{QuestionJSON: strings.TrimSpace(string(data)), SessionID: e.SessionID}
	}
	return nil
}

func (r *GeminiRunner) execOnce(ctx context.Context, args []string, workingDir, projectDir string, e *storage.Execution) error {
	// Temporarily bypass external command execution to debug pipe.
	// We will simulate outputting to stdoutW directly.

	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)
	}

	// Simulate writing to stdoutW
	go func() {
		defer stdoutW.Close() // Close the writer when done.
		fmt.Fprintf(stdoutW, "```json\n")
		fmt.Fprintf(stdoutW, "{\"type\":\"content_block_start\",\"content_block\":{\"text\":\"Hello, Gemini!\",\"type\":\"text\"}}\n")
		fmt.Fprintf(stdoutW, "{\"type\":\"content_block_delta\",\"content_block\":{\"text\":\" How are you?\"}}\n")
		fmt.Fprintf(stdoutW, "{\"type\":\"content_block_end\"}\n")
		fmt.Fprintf(stdoutW, "{\"type\":\"message_delta\",\"message\":{\"role\":\"model\"}}\n")
		fmt.Fprintf(stdoutW, "{\"type\":\"message_end\"}\n")
		fmt.Fprintf(stdoutW, "```\n")
	}()


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

	wg.Wait() // Wait for parseGeminiStream to finish

	// Set a dummy exit code for this simulated run
	e.ExitCode = 0

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

// parseGeminiStream reads streaming JSON from the gemini CLI, unwraps markdown
// code blocks, writes the inner JSON to w, and returns (costUSD, error).
// For now, it focuses on unwrapping and writing, not detailed parsing of cost/errors.
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))

	// Default: write raw content as-is (preserves trailing newline).
	jsonContent := string(fullOutput)

	// Unwrap markdown code fences if present.
	trimmed := strings.TrimSpace(jsonContent)
	if jsonStartIdx := strings.Index(trimmed, "```json"); jsonStartIdx != -1 {
		if jsonEndIdx := strings.LastIndex(trimmed, "```"); jsonEndIdx != -1 && jsonEndIdx > jsonStartIdx {
			inner := trimmed[jsonStartIdx+len("```json") : jsonEndIdx]
			jsonContent = strings.TrimSpace(inner) + "\n"
		} else {
			logger.Warn("malformed markdown JSON block from Gemini, falling back to raw output", "outputLength", len(jsonContent))
		}
	}

	// Write the (possibly extracted) JSON content to the writer.
	if _, writeErr := w.Write([]byte(jsonContent)); writeErr != nil {
		return 0, fmt.Errorf("writing extracted gemini json: %w", writeErr)
	}

	// Parse each line for result type to extract cost and execution errors.
	var resultErr error
	var costUSD float64
	for _, line := range strings.Split(jsonContent, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		var msg 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), &msg); err != nil {
			continue
		}
		if msg.Type == "result" {
			costUSD = msg.Cost
			if msg.IsError {
				resultErr = fmt.Errorf("gemini execution error: %s", msg.Result)
			}
		}
	}

	return costUSD, resultErr
}

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
}