package daemon

import (
	"bytes"
	"context"
	"crypto/sha256"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"banger/internal/firecracker"
	"banger/internal/guest"
	"banger/internal/hostnat"
	"banger/internal/model"
	"banger/internal/system"
	"banger/internal/vsockagent"
)

const (
	defaultMiseVersion      = "v2025.12.0"
	defaultMiseInstallPath  = "/usr/local/bin/mise"
	defaultMiseActivateLine = `eval "$(/usr/local/bin/mise activate bash)"`
	defaultOpenCodeTool     = "github:anomalyco/opencode"
	defaultTPMRepo          = "https://github.com/tmux-plugins/tpm"
	defaultResurrectRepo    = "https://github.com/tmux-plugins/tmux-resurrect"
	defaultContinuumRepo    = "https://github.com/tmux-plugins/tmux-continuum"
	defaultTMUXPluginDir    = "/root/.tmux/plugins"
	defaultTMUXResurrectDir = "/root/.tmux/resurrect"
	tmuxManagedBlockStart   = "# >>> banger tmux plugins >>>"
	tmuxManagedBlockEnd     = "# <<< banger tmux plugins <<<"
)

type imageBuildSpec struct {
	ID            string
	Name          string
	BaseRootfs    string
	RootfsPath    string
	BuildLog      io.Writer
	KernelPath    string
	InitrdPath    string
	ModulesDir    string
	PackagesPath  string
	InstallDocker bool
	Size          string
}

type imageBuildVM struct {
	Name      string
	GuestIP   string
	TapDevice string
	APISock   string
	PID       int
}

func (d *Daemon) runImageBuild(ctx context.Context, spec imageBuildSpec) error {
	if d.imageBuild != nil {
		return d.imageBuild(ctx, spec)
	}
	return d.runImageBuildNative(ctx, spec)
}

func (d *Daemon) runImageBuildNative(ctx context.Context, spec imageBuildSpec) (err error) {
	packages, err := system.ReadNormalizedLines(spec.PackagesPath)
	if err != nil {
		return err
	}
	if err := system.CopyFilePreferClone(spec.BaseRootfs, spec.RootfsPath); err != nil {
		return err
	}
	if spec.Size != "" {
		if err := resizeRootfs(spec.BaseRootfs, spec.RootfsPath, spec.Size); err != nil {
			return err
		}
	}

	vm, cleanup, err := d.startImageBuildVM(ctx, spec)
	if err != nil {
		return err
	}
	defer func() {
		cleanupErr := cleanup(context.Background())
		if cleanupErr != nil {
			err = errors.Join(err, cleanupErr)
		}
	}()

	sshAddress := vm.GuestIP + ":22"
	if _, err := fmt.Fprintf(spec.BuildLog, "[image.build] waiting for ssh on %s\n", sshAddress); err != nil {
		return err
	}
	waitCtx, cancel := context.WithTimeout(ctx, 60*time.Second)
	defer cancel()
	if err := guest.WaitForSSH(waitCtx, sshAddress, d.config.SSHKeyPath, time.Second); err != nil {
		return err
	}

	client, err := guest.Dial(ctx, sshAddress, d.config.SSHKeyPath)
	if err != nil {
		return err
	}
	defer client.Close()

	helperBytes, err := os.ReadFile(d.config.VSockAgentPath)
	if err != nil {
		return err
	}
	if err := writeBuildLog(spec.BuildLog, "installing vsock agent"); err != nil {
		return err
	}
	if err := client.UploadFile(ctx, vsockagent.GuestInstallPath, 0o755, helperBytes, spec.BuildLog); err != nil {
		return err
	}
	if err := writeBuildLog(spec.BuildLog, "configuring guest"); err != nil {
		return err
	}
	if err := client.RunScript(ctx, buildProvisionScript(vm.Name, d.config.DefaultDNS, packages, spec.InstallDocker), spec.BuildLog); err != nil {
		return err
	}
	if strings.TrimSpace(spec.ModulesDir) != "" {
		if err := writeBuildLog(spec.BuildLog, "copying kernel modules"); err != nil {
			return err
		}
		if err := client.StreamTar(ctx, spec.ModulesDir, buildModulesCommand(filepath.Base(spec.ModulesDir)), spec.BuildLog); err != nil {
			return err
		}
	}
	if err := writeBuildLog(spec.BuildLog, "shutting down guest"); err != nil {
		return err
	}
	if err := client.RunScript(ctx, "set -e\nsync\n", spec.BuildLog); err != nil {
		return err
	}
	return d.shutdownImageBuildVM(ctx, vm)
}

func resizeRootfs(baseRootfs, rootfsPath, sizeSpec string) error {
	sizeBytes, err := model.ParseSize(sizeSpec)
	if err != nil {
		return err
	}
	info, err := os.Stat(baseRootfs)
	if err != nil {
		return err
	}
	if sizeBytes < info.Size() {
		return fmt.Errorf("size must be >= base image size")
	}
	return system.ResizeExt4Image(context.Background(), system.NewRunner(), rootfsPath, sizeBytes)
}

func (d *Daemon) startImageBuildVM(ctx context.Context, spec imageBuildSpec) (imageBuildVM, func(context.Context) error, error) {
	if err := d.ensureBridge(ctx); err != nil {
		return imageBuildVM{}, nil, err
	}
	if err := d.ensureSocketDir(); err != nil {
		return imageBuildVM{}, nil, err
	}
	fcPath, err := d.firecrackerBinary()
	if err != nil {
		return imageBuildVM{}, nil, err
	}

	shortID := system.ShortID(spec.ID)
	guestIP, err := d.store.NextGuestIP(ctx, bridgePrefix(d.config.BridgeIP))
	if err != nil {
		return imageBuildVM{}, nil, err
	}
	vm := imageBuildVM{
		Name:      "image-build-" + shortID,
		GuestIP:   guestIP,
		TapDevice: "tap-img-" + shortID,
		APISock:   filepath.Join(d.layout.RuntimeDir, "img-"+shortID+".sock"),
	}
	if err := os.RemoveAll(vm.APISock); err != nil && !os.IsNotExist(err) {
		return imageBuildVM{}, nil, err
	}
	if err := d.createTap(ctx, vm.TapDevice); err != nil {
		return imageBuildVM{}, nil, err
	}
	if err := hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, true); err != nil {
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}

	firecrackerCtx := context.Background()
	machine, err := firecracker.NewMachine(firecrackerCtx, firecracker.MachineConfig{
		BinaryPath:      fcPath,
		VMID:            spec.ID,
		SocketPath:      vm.APISock,
		LogPath:         spec.RootfsPath + ".firecracker.log",
		MetricsPath:     filepath.Join(filepath.Dir(spec.RootfsPath), "metrics.json"),
		KernelImagePath: spec.KernelPath,
		InitrdPath:      spec.InitrdPath,
		KernelArgs:      system.BuildBootArgs(vm.Name, vm.GuestIP, d.config.BridgeIP, d.config.DefaultDNS),
		Drives: []firecracker.DriveConfig{{
			ID:       "rootfs",
			Path:     spec.RootfsPath,
			ReadOnly: false,
			IsRoot:   true,
		}},
		TapDevice: vm.TapDevice,
		VCPUCount: model.DefaultVCPUCount,
		MemoryMiB: model.DefaultMemoryMiB,
		Logger:    d.logger,
	})
	if err != nil {
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}
	if err := machine.Start(firecrackerCtx); err != nil {
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}
	vm.PID = d.resolveFirecrackerPID(firecrackerCtx, machine, vm.APISock)
	if err := d.ensureSocketAccess(ctx, vm.APISock, "firecracker api socket"); err != nil {
		_ = d.killVMProcess(context.Background(), vm.PID)
		_ = hostnat.Ensure(ctx, d.runner, vm.GuestIP, vm.TapDevice, false)
		_, _ = d.runner.RunSudo(ctx, "ip", "link", "del", vm.TapDevice)
		return imageBuildVM{}, nil, err
	}

	cleanup := func(cleanupCtx context.Context) error {
		if vm.PID > 0 && system.ProcessRunning(vm.PID, vm.APISock) {
			_ = d.killVMProcess(cleanupCtx, vm.PID)
			_ = d.waitForExit(cleanupCtx, vm.PID, vm.APISock, 10*time.Second)
		}
		_ = hostnat.Ensure(cleanupCtx, d.runner, vm.GuestIP, vm.TapDevice, false)
		if vm.TapDevice != "" {
			_, _ = d.runner.RunSudo(cleanupCtx, "ip", "link", "del", vm.TapDevice)
		}
		if vm.APISock != "" {
			_ = os.Remove(vm.APISock)
		}
		return nil
	}
	return vm, cleanup, nil
}

func (d *Daemon) shutdownImageBuildVM(ctx context.Context, vm imageBuildVM) error {
	buildVM := model.VMRecord{Runtime: model.VMRuntime{APISockPath: vm.APISock}}
	if err := d.sendCtrlAltDel(ctx, buildVM); err != nil {
		return err
	}
	return d.waitForExit(ctx, vm.PID, vm.APISock, 15*time.Second)
}

func buildProvisionScript(vmName, dnsServer string, packages []string, installDocker bool) string {
	var script bytes.Buffer
	script.WriteString("set -euo pipefail\n")
	fmt.Fprintf(&script, "printf 'nameserver %%s\\n' %s > /etc/resolv.conf\n", shellQuote(dnsServer))
	fmt.Fprintf(&script, "printf '%%s\\n' %s > /etc/hostname\n", shellQuote(vmName))
	fmt.Fprintf(&script, "printf '127.0.0.1 localhost\\n127.0.1.1 %%s\\n' %s > /etc/hosts\n", shellQuote(vmName))
	script.WriteString("touch /etc/fstab\n")
	script.WriteString("sed -i '\\|^/dev/vdb[[:space:]]\\+/home[[:space:]]|d; \\|^/dev/vdc[[:space:]]\\+/var[[:space:]]|d' /etc/fstab\n")
	script.WriteString("if ! grep -q '^tmpfs /run ' /etc/fstab; then echo 'tmpfs /run tmpfs defaults,nodev,nosuid,mode=0755 0 0' >> /etc/fstab; fi\n")
	script.WriteString("if ! grep -q '^tmpfs /tmp ' /etc/fstab; then echo 'tmpfs /tmp tmpfs defaults,nodev,nosuid,mode=1777 0 0' >> /etc/fstab; fi\n")
	script.WriteString("apt-get update\n")
	script.WriteString("DEBIAN_FRONTEND=noninteractive apt-get -y upgrade\n")
	fmt.Fprintf(&script, "PACKAGES=%s\n", shellArray(packages))
	script.WriteString("DEBIAN_FRONTEND=noninteractive apt-get -y install \"${PACKAGES[@]}\"\n")
	appendMiseSetup(&script)
	appendTmuxSetup(&script)
	appendVSockPingSetup(&script)
	if installDocker {
		script.WriteString("DEBIAN_FRONTEND=noninteractive apt-get -y remove containerd || true\n")
		script.WriteString("if ! DEBIAN_FRONTEND=noninteractive apt-get -y install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin; then\n")
		script.WriteString("  DEBIAN_FRONTEND=noninteractive apt-get -y install docker.io\n")
		script.WriteString("fi\n")
		script.WriteString("if command -v systemctl >/dev/null 2>&1; then systemctl enable --now docker || true; fi\n")
	}
	appendGuestCleanup(&script)
	script.WriteString("git config --system init.defaultBranch main\n")
	return script.String()
}

func buildModulesCommand(modulesBase string) string {
	return fmt.Sprintf("bash -se <<'EOF'\nset -euo pipefail\nmkdir -p /lib/modules\ntar -C /lib/modules -xf -\ndepmod -a %s\nmkdir -p /etc/modules-load.d\nprintf 'nf_tables\\nnft_chain_nat\\nveth\\nbr_netfilter\\noverlay\\n' > /etc/modules-load.d/docker-netfilter.conf\nmkdir -p /etc/sysctl.d\ncat > /etc/sysctl.d/99-docker.conf <<'SYSCTL'\nnet.bridge.bridge-nf-call-iptables = 1\nnet.bridge.bridge-nf-call-ip6tables = 1\nnet.ipv4.ip_forward = 1\nSYSCTL\nsysctl --system >/dev/null 2>&1 || true\nEOF", shellQuote(modulesBase))
}

func appendMiseSetup(script *bytes.Buffer) {
	fmt.Fprintf(script, "curl -fsSL https://mise.run | MISE_INSTALL_PATH=%s MISE_VERSION=%s sh\n", shellQuote(defaultMiseInstallPath), shellQuote(defaultMiseVersion))
	fmt.Fprintf(script, "%s use -g %s\n", shellQuote(defaultMiseInstallPath), shellQuote(defaultOpenCodeTool))
	script.WriteString("mkdir -p /etc/profile.d\n")
	script.WriteString("cat > /etc/profile.d/mise.sh <<'EOF'\n")
	fmt.Fprintf(script, "if [ -n \"${BASH_VERSION:-}\" ] && [ -x %s ]; then\n", shellQuote(defaultMiseInstallPath))
	fmt.Fprintf(script, "  %s\n", defaultMiseActivateLine)
	script.WriteString("fi\n")
	script.WriteString("EOF\n")
	script.WriteString("chmod 0644 /etc/profile.d/mise.sh\n")
	appendLineIfMissing(script, "/etc/bash.bashrc", defaultMiseActivateLine)
}

func appendTmuxSetup(script *bytes.Buffer) {
	fmt.Fprintf(script, "TMUX_PLUGIN_DIR=%s\n", shellQuote(defaultTMUXPluginDir))
	fmt.Fprintf(script, "TMUX_RESURRECT_DIR=%s\n", shellQuote(defaultTMUXResurrectDir))
	script.WriteString("mkdir -p \"$TMUX_PLUGIN_DIR\" \"$TMUX_RESURRECT_DIR\"\n")
	appendGitRepo(script, "$TMUX_PLUGIN_DIR/tpm", defaultTPMRepo)
	appendGitRepo(script, "$TMUX_PLUGIN_DIR/tmux-resurrect", defaultResurrectRepo)
	appendGitRepo(script, "$TMUX_PLUGIN_DIR/tmux-continuum", defaultContinuumRepo)
	script.WriteString("TMUX_CONF=/root/.tmux.conf\n")
	fmt.Fprintf(script, "TMUX_MANAGED_START=%s\n", shellQuote(tmuxManagedBlockStart))
	fmt.Fprintf(script, "TMUX_MANAGED_END=%s\n", shellQuote(tmuxManagedBlockEnd))
	script.WriteString("tmp_tmux_conf=$(mktemp)\n")
	script.WriteString("if [[ -f \"$TMUX_CONF\" ]]; then\n")
	script.WriteString("  awk -v begin=\"$TMUX_MANAGED_START\" -v end=\"$TMUX_MANAGED_END\" '$0 == begin { skip = 1; next } $0 == end { skip = 0; next } !skip { print }' \"$TMUX_CONF\" > \"$tmp_tmux_conf\"\n")
	script.WriteString("else\n")
	script.WriteString("  : > \"$tmp_tmux_conf\"\n")
	script.WriteString("fi\n")
	script.WriteString("if [[ -s \"$tmp_tmux_conf\" ]]; then\n")
	script.WriteString("  printf '\\n' >> \"$tmp_tmux_conf\"\n")
	script.WriteString("fi\n")
	script.WriteString("cat >> \"$tmp_tmux_conf\" <<'EOF'\n")
	script.WriteString(tmuxManagedBlockStart + "\n")
	script.WriteString("set -g @plugin 'tmux-plugins/tpm'\n")
	script.WriteString("set -g @plugin 'tmux-plugins/tmux-resurrect'\n")
	script.WriteString("set -g @plugin 'tmux-plugins/tmux-continuum'\n")
	script.WriteString("set -g @continuum-save-interval '15'\n")
	script.WriteString("set -g @continuum-restore 'off'\n")
	script.WriteString("set -g @resurrect-dir '/root/.tmux/resurrect'\n")
	script.WriteString("run '~/.tmux/plugins/tpm/tpm'\n")
	script.WriteString(tmuxManagedBlockEnd + "\n")
	script.WriteString("EOF\n")
	script.WriteString("mv \"$tmp_tmux_conf\" \"$TMUX_CONF\"\n")
	script.WriteString("chmod 0644 \"$TMUX_CONF\"\n")
}

func appendVSockPingSetup(script *bytes.Buffer) {
	script.WriteString("mkdir -p /etc/modules-load.d /etc/systemd/system\n")
	script.WriteString("cat > /etc/modules-load.d/banger-vsock.conf <<'EOF'\n")
	script.WriteString(vsockagent.ModulesLoadConfig())
	script.WriteString("EOF\n")
	script.WriteString("chmod 0644 /etc/modules-load.d/banger-vsock.conf\n")
	script.WriteString("cat > /etc/systemd/system/" + vsockagent.ServiceName + " <<'EOF'\n")
	script.WriteString(vsockagent.ServiceUnit())
	script.WriteString("EOF\n")
	script.WriteString("chmod 0644 /etc/systemd/system/" + vsockagent.ServiceName + "\n")
	script.WriteString("if command -v systemctl >/dev/null 2>&1; then systemctl daemon-reload || true; systemctl enable --now " + vsockagent.ServiceName + " || true; fi\n")
}

func appendGitRepo(script *bytes.Buffer, dir, repo string) {
	fmt.Fprintf(script, "if [[ -d \"%s/.git\" ]]; then\n", dir)
	fmt.Fprintf(script, "  git -C \"%s\" fetch --depth 1 origin\n", dir)
	fmt.Fprintf(script, "  git -C \"%s\" reset --hard FETCH_HEAD\n", dir)
	script.WriteString("else\n")
	fmt.Fprintf(script, "  rm -rf \"%s\"\n", dir)
	fmt.Fprintf(script, "  git clone --depth 1 %s \"%s\"\n", shellQuote(repo), dir)
	script.WriteString("fi\n")
}

func appendGuestCleanup(script *bytes.Buffer) {
	script.WriteString("rm -f /root/get-docker /root/get-docker.sh /tmp/get-docker /tmp/get-docker.sh\n")
}

func appendLineIfMissing(script *bytes.Buffer, path, line string) {
	fmt.Fprintf(script, "touch %s\n", shellQuote(path))
	fmt.Fprintf(script, "if ! grep -Fqx %s %s; then\n", shellQuote(line), shellQuote(path))
	fmt.Fprintf(script, "  printf '\\n%%s\\n' %s >> %s\n", shellQuote(line), shellQuote(path))
	script.WriteString("fi\n")
}

func shellArray(values []string) string {
	quoted := make([]string, 0, len(values))
	for _, value := range values {
		quoted = append(quoted, shellQuote(value))
	}
	return "(" + strings.Join(quoted, " ") + ")"
}

func shellQuote(value string) string {
	return "'" + strings.ReplaceAll(value, "'", `'"'"'`) + "'"
}

func writeBuildLog(w io.Writer, message string) error {
	if w == nil {
		return nil
	}
	_, err := fmt.Fprintf(w, "[image.build] %s\n", message)
	return err
}

func packagesHash(lines []string) string {
	sum := sha256.Sum256([]byte(strings.Join(lines, "\n") + "\n"))
	return fmt.Sprintf("%x", sum)
}