package daemon

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"net"
	"strings"
	"time"

	"banger/internal/api"
	sess "banger/internal/daemon/session"
	"banger/internal/guest"
	"banger/internal/model"
)

func (d *Daemon) StartGuestSession(ctx context.Context, params api.GuestSessionStartParams) (model.GuestSession, error) {
	stdinMode := model.GuestSessionStdinMode(strings.TrimSpace(params.StdinMode))
	if stdinMode == "" {
		stdinMode = model.GuestSessionStdinClosed
	}
	if stdinMode != model.GuestSessionStdinClosed && stdinMode != model.GuestSessionStdinPipe {
		return model.GuestSession{}, fmt.Errorf("unsupported stdin mode %q", params.StdinMode)
	}
	if strings.TrimSpace(params.Command) == "" {
		return model.GuestSession{}, errors.New("session command is required")
	}
	var created model.GuestSession
	_, err := d.withVMLockByRef(ctx, params.VMIDOrName, func(vm model.VMRecord) (model.VMRecord, error) {
		if !d.vmAlive(vm) {
			return model.VMRecord{}, fmt.Errorf("vm %q is not running", vm.Name)
		}
		session, err := d.startGuestSessionLocked(ctx, vm, params, stdinMode)
		if err != nil {
			return model.VMRecord{}, err
		}
		created = session
		return vm, nil
	})
	return created, err
}

func (d *Daemon) startGuestSessionLocked(ctx context.Context, vm model.VMRecord, params api.GuestSessionStartParams, stdinMode model.GuestSessionStdinMode) (model.GuestSession, error) {
	id, err := model.NewID()
	if err != nil {
		return model.GuestSession{}, err
	}
	now := model.Now()
	session := model.GuestSession{
		ID:            id,
		VMID:          vm.ID,
		Name:          sess.DefaultName(id, params.Command, params.Name),
		Backend:       sess.BackendSSH,
		Command:       params.Command,
		Args:          append([]string(nil), params.Args...),
		CWD:           strings.TrimSpace(params.CWD),
		Env:           sess.CloneStringMap(params.Env),
		StdinMode:     stdinMode,
		Status:        model.GuestSessionStatusStarting,
		GuestStateDir: sess.StateDir(id),
		StdoutLogPath: sess.StdoutLogPath(id),
		StderrLogPath: sess.StderrLogPath(id),
		Tags:          sess.CloneStringMap(params.Tags),
		Attachable:    stdinMode == model.GuestSessionStdinPipe,
		Reattachable:  stdinMode == model.GuestSessionStdinPipe,
		CreatedAt:     now,
		UpdatedAt:     now,
	}
	if session.Attachable {
		session.AttachBackend = sess.AttachBackendSSHBridge
		session.AttachMode = sess.AttachModeExclusive
	} else {
		session.AttachBackend = sess.AttachBackendNone
	}
	if err := d.store.UpsertGuestSession(ctx, session); err != nil {
		return model.GuestSession{}, err
	}
	fail := func(stage, message, rawLog string) (model.GuestSession, error) {
		session = sess.FailLaunch(session, stage, message, rawLog)
		if err := d.store.UpsertGuestSession(ctx, session); err != nil {
			return model.GuestSession{}, err
		}
		return session, nil
	}
	address := net.JoinHostPort(vm.Runtime.GuestIP, "22")
	if err := d.waitForGuestSSH(ctx, address, 250*time.Millisecond); err != nil {
		return fail("ssh_unavailable", fmt.Sprintf("guest ssh unavailable: %v", err), "")
	}
	client, err := d.dialGuest(ctx, address)
	if err != nil {
		return fail("dial_guest", fmt.Sprintf("dial guest ssh: %v", err), "")
	}
	defer client.Close()
	var preflightLog bytes.Buffer
	if err := client.RunScript(ctx, sess.CWDPreflightScript(session.CWD), &preflightLog); err != nil {
		return fail("preflight_cwd", fmt.Sprintf("guest working directory is unavailable: %s", sess.DefaultCWD(session.CWD)), preflightLog.String())
	}
	preflightLog.Reset()
	requiredCommands := sess.NormalizeRequiredCommands(params.Command, params.RequiredCommands)
	if err := client.RunScript(ctx, sess.CommandPreflightScript(requiredCommands), &preflightLog); err != nil {
		return fail("preflight_command", fmt.Sprintf("required guest command is unavailable: %s", strings.TrimSpace(preflightLog.String())), preflightLog.String())
	}
	var uploadLog bytes.Buffer
	if err := client.UploadFile(ctx, sess.ScriptPath(id), 0o755, []byte(sess.Script(session)), &uploadLog); err != nil {
		return fail("upload_script", "upload guest session script failed", uploadLog.String())
	}
	var launchLog bytes.Buffer
	launchScript := fmt.Sprintf("set -euo pipefail\nnohup bash %s >/dev/null 2>&1 </dev/null &\ndisown || true\n", sess.ShellQuote(sess.ScriptPath(id)))
	if err := client.RunScript(ctx, launchScript, &launchLog); err != nil {
		return fail("launch", "launch guest session failed", launchLog.String())
	}
	readyCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()
	updated, err := d.waitForGuestSessionReadyHook(readyCtx, vm, session)
	if err != nil {
		return fail("ready_wait", "guest session did not report ready state", err.Error())
	}
	session = updated
	if session.Status == model.GuestSessionStatusStarting {
		session.Status = model.GuestSessionStatusRunning
		session.StartedAt = model.Now()
		session.UpdatedAt = model.Now()
	}
	session.LaunchStage = ""
	session.LaunchMessage = ""
	session.LaunchRawLog = ""
	session.LastError = ""
	if err := d.store.UpsertGuestSession(ctx, session); err != nil {
		return model.GuestSession{}, err
	}
	return session, nil
}

func (d *Daemon) GetGuestSession(ctx context.Context, params api.GuestSessionRefParams) (model.GuestSession, error) {
	vm, err := d.FindVM(ctx, params.VMIDOrName)
	if err != nil {
		return model.GuestSession{}, err
	}
	session, err := d.findGuestSession(ctx, vm.ID, params.SessionIDOrName)
	if err != nil {
		return model.GuestSession{}, err
	}
	return d.refreshGuestSession(ctx, vm, session)
}

func (d *Daemon) ListGuestSessions(ctx context.Context, params api.VMRefParams) ([]model.GuestSession, error) {
	vm, err := d.FindVM(ctx, params.IDOrName)
	if err != nil {
		return nil, err
	}
	sessions, err := d.store.ListGuestSessionsByVM(ctx, vm.ID)
	if err != nil {
		return nil, err
	}
	for index := range sessions {
		refreshed, refreshErr := d.refreshGuestSession(ctx, vm, sessions[index])
		if refreshErr == nil {
			sessions[index] = refreshed
		}
	}
	return sessions, nil
}

func (d *Daemon) StopGuestSession(ctx context.Context, params api.GuestSessionRefParams) (model.GuestSession, error) {
	return d.signalGuestSession(ctx, params, "TERM")
}

func (d *Daemon) KillGuestSession(ctx context.Context, params api.GuestSessionRefParams) (model.GuestSession, error) {
	return d.signalGuestSession(ctx, params, "KILL")
}

func (d *Daemon) signalGuestSession(ctx context.Context, params api.GuestSessionRefParams, signal string) (model.GuestSession, error) {
	vm, err := d.FindVM(ctx, params.VMIDOrName)
	if err != nil {
		return model.GuestSession{}, err
	}
	session, err := d.findGuestSession(ctx, vm.ID, params.SessionIDOrName)
	if err != nil {
		return model.GuestSession{}, err
	}
	session, _ = d.refreshGuestSession(ctx, vm, session)
	if session.Status == model.GuestSessionStatusExited || session.Status == model.GuestSessionStatusFailed {
		return session, nil
	}
	if !d.vmAlive(vm) {
		session.Status = model.GuestSessionStatusFailed
		session.LastError = "vm is not running"
		now := model.Now()
		session.UpdatedAt = now
		session.EndedAt = now
		session.Attachable = false
		if err := d.store.UpsertGuestSession(ctx, session); err != nil {
			return model.GuestSession{}, err
		}
		return session, nil
	}
	client, err := guest.Dial(ctx, net.JoinHostPort(vm.Runtime.GuestIP, "22"), d.config.SSHKeyPath)
	if err != nil {
		return model.GuestSession{}, err
	}
	defer client.Close()
	var log bytes.Buffer
	if err := client.RunScript(ctx, sess.SignalScript(session.ID, signal), &log); err != nil {
		return model.GuestSession{}, sess.FormatStepError("signal guest session", err, log.String())
	}
	session.Status = model.GuestSessionStatusStopping
	session.UpdatedAt = model.Now()
	if err := d.store.UpsertGuestSession(ctx, session); err != nil {
		return model.GuestSession{}, err
	}
	return session, nil
}