package session

import (
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/warrenronsiek/ctask/internal/shell"
)

// LaunchOpts configures a session launch.
type LaunchOpts struct {
	WsDir   string
	EnvVars map[string]string
	Agent   string
	Mode    string
	Slug    string
	Shell   bool // true = interactive shell, false = agent

	// Force suppresses both the active-session warning (Layer 1) and the
	// stale-workspace warning (Layer 3). It does NOT disable the metadata
	// write lock or the session summary. Used for scripted/automated runs.
	Force bool
}

// manifestStartPath returns the path to the start manifest file.
func manifestStartPath(wsDir string) string {
	return filepath.Join(wsDir, ".ctask", "manifest-start.json")
}

// Run launches an agent or shell session with pre/post manifest capture and session logging.
// Returns the child process error (for exit code propagation).
func Run(opts LaunchOpts) error {
	startTime := time.Now().UTC().Truncate(time.Second)

	// Pre-session: capture start manifest
	startManifest, err := CaptureManifest(opts.WsDir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "[ctask] warning: failed to capture start manifest: %v\n", err)
		// Continue anyway -- never block the user
	}

	if startManifest != nil {
		mPath := manifestStartPath(opts.WsDir)
		if err := WriteManifest(mPath, startManifest); err != nil {
			fmt.Fprintf(os.Stderr, "[ctask] warning: failed to write start manifest: %v\n", err)
		}
	}

	// Launch the session
	var childErr error
	if opts.Shell {
		childErr = shell.ExecShell(opts.WsDir, opts.EnvVars, opts.Slug, opts.Mode)
	} else {
		// Print banner before agent launch
		for _, line := range shell.BannerLines(opts.Mode, opts.Slug, opts.WsDir) {
			fmt.Println(line)
		}
		childErr = shell.ExecAgent(opts.Agent, opts.WsDir, opts.EnvVars)
	}

	// Post-session: capture end manifest and log
	endTime := time.Now().UTC().Truncate(time.Second)

	if startManifest != nil {
		if logErr := captureAndLog(opts, startManifest, startTime, endTime); logErr != nil {
			fmt.Fprintf(os.Stderr, "[ctask] warning: session logging failed: %v\n", logErr)
			// Keep manifest-start.json for debugging
		} else {
			// Clean up manifest-start.json on success
			os.Remove(manifestStartPath(opts.WsDir))
		}
	}

	return childErr
}

// captureAndLog captures the end manifest, diffs, and appends to session log.
func captureAndLog(opts LaunchOpts, startManifest *Manifest, startTime, endTime time.Time) error {
	endManifest, err := CaptureManifest(opts.WsDir)
	if err != nil {
		return fmt.Errorf("capturing end manifest: %w", err)
	}

	diff := DiffManifests(startManifest, endManifest)

	info := &SessionInfo{
		Agent:     opts.Agent,
		Mode:      opts.Mode,
		StartTime: startTime,
		EndTime:   endTime,
		Diff:      diff,
	}

	// For shell sessions, record "shell" as agent
	if opts.Shell {
		info.Agent = "shell"
	}

	if err := AppendSessionLog(opts.WsDir, info); err != nil {
		return fmt.Errorf("appending session log: %w", err)
	}

	return nil
}