package daemon

import (
	"context"
	"fmt"
	"strings"

	"banger/internal/config"
	"banger/internal/model"
	"banger/internal/paths"
	"banger/internal/system"
)

func Doctor(ctx context.Context) (system.Report, error) {
	layout, err := paths.Resolve()
	if err != nil {
		return system.Report{}, err
	}
	cfg, err := config.Load(layout)
	if err != nil {
		return system.Report{}, err
	}
	d := &Daemon{
		layout: layout,
		config: cfg,
		runner: system.NewRunner(),
	}
	return d.doctorReport(ctx), nil
}

func (d *Daemon) doctorReport(ctx context.Context) system.Report {
	report := system.Report{}

	report.AddPreflight("runtime bundle", d.runtimeBundleChecks(), runtimeBundleStatus(d.config))
	report.AddPreflight("core vm lifecycle", d.coreVMLifecycleChecks(), "required host tools available")
	report.AddPreflight("vsock guest agent", d.vsockChecks(), "vsock agent prerequisites available")
	d.addCapabilityDoctorChecks(ctx, &report)
	report.AddPreflight("image build", d.imageBuildChecks(ctx), "image build prerequisites available")

	return report
}

func (d *Daemon) runtimeBundleChecks() *system.Preflight {
	checks := system.NewPreflight()
	hint := paths.RuntimeBundleHint()
	checks.RequireExecutable(d.config.FirecrackerBin, "firecracker binary", hint)
	checks.RequireFile(d.config.SSHKeyPath, "runtime ssh private key", `refresh the runtime bundle`)
	checks.RequireExecutable(d.config.VSockAgentPath, "vsock agent", `run 'make build' or refresh the runtime bundle`)
	checks.RequireFile(d.config.DefaultRootfs, "default rootfs image", `set "default_rootfs" or refresh the runtime bundle`)
	checks.RequireFile(d.config.DefaultKernel, "kernel image", `set "default_kernel" or refresh the runtime bundle`)
	if strings.TrimSpace(d.config.DefaultInitrd) != "" {
		checks.RequireFile(d.config.DefaultInitrd, "initrd image", `set "default_initrd" or refresh the runtime bundle`)
	}
	if strings.TrimSpace(d.config.DefaultPackagesFile) != "" {
		checks.RequireFile(d.config.DefaultPackagesFile, "package manifest", `set "default_packages_file" or refresh the runtime bundle`)
	}
	return checks
}

func (d *Daemon) coreVMLifecycleChecks() *system.Preflight {
	checks := system.NewPreflight()
	d.addBaseStartCommandPrereqs(checks)
	return checks
}

func (d *Daemon) imageBuildChecks(ctx context.Context) *system.Preflight {
	checks := system.NewPreflight()
	d.addImageBuildPrereqs(
		ctx,
		checks,
		firstNonEmpty(d.config.DefaultBaseRootfs, d.config.DefaultRootfs),
		d.config.DefaultKernel,
		d.config.DefaultInitrd,
		d.config.DefaultModulesDir,
		"",
	)
	return checks
}

func (d *Daemon) vsockChecks() *system.Preflight {
	checks := system.NewPreflight()
	checks.RequireExecutable(d.config.VSockAgentPath, "vsock agent", `run 'make build' or refresh the runtime bundle`)
	checks.RequireFile(vsockHostDevicePath, "vsock host device", "load the vhost_vsock kernel module on the host")
	return checks
}

func runtimeBundleStatus(cfg model.DaemonConfig) string {
	if strings.TrimSpace(cfg.RuntimeDir) == "" {
		return "runtime dir not configured"
	}
	return fmt.Sprintf("runtime dir %s", cfg.RuntimeDir)
}

func firstNonEmpty(values ...string) string {
	for _, value := range values {
		if strings.TrimSpace(value) != "" {
			return value
		}
	}
	return ""
}