// Copyright (c) 2026 Sidero Labs, Inc.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.

// Package kernelargs contains logic and utilities for managing extra kernel arguments.
package kernelargs

import (
	"context"
	"fmt"
	"slices"
	"strings"

	"github.com/blang/semver/v4"
	"github.com/cosi-project/runtime/pkg/controller"
	"github.com/cosi-project/runtime/pkg/resource"
	"github.com/cosi-project/runtime/pkg/state"
	"github.com/siderolabs/gen/xslices"
	"github.com/siderolabs/talos/pkg/machinery/constants"
	"go.uber.org/zap"

	"github.com/siderolabs/omni/client/pkg/omni/resources/omni"
)

type Initializer struct {
	state  state.State
	logger *zap.Logger
}

func NewInitializer(state state.State, logger *zap.Logger) (*Initializer, error) {
	if state == nil {
		return nil, fmt.Errorf("state is nil")
	}

	if logger == nil {
		logger = zap.NewNop()
	}

	return &Initializer{
		state:  state,
		logger: logger,
	}, nil
}

func (initializer *Initializer) Init(ctx context.Context, id resource.ID, args []string) error {
	extraArgs := xslices.Filter(args, func(value string) bool { return !isProtected(value) })

	if len(extraArgs) == 0 {
		return nil
	}

	kernelArgs := omni.NewKernelArgs(id)
	kernelArgs.TypedSpec().Value.Args = extraArgs

	if err := initializer.state.Create(ctx, kernelArgs); err != nil && !state.IsConflictError(err) {
		return fmt.Errorf("error creating extra kernel args configuration: %w", err)
	}

	return nil
}

func UpdateSupported(machineStatus *omni.MachineStatus, getClusterMachineConfig func() (*omni.ClusterMachineConfig, error)) (bool, error) {
	securityState := machineStatus.TypedSpec().Value.SecurityState
	talosVersion := machineStatus.TypedSpec().Value.TalosVersion

	if securityState == nil && talosVersion == "" {
		return false, fmt.Errorf("missing security state and Talos version")
	}

	if securityState != nil && securityState.BootedWithUki {
		return true, nil
	}

	parsedTalosVersion, err := semver.ParseTolerant(talosVersion)
	if err != nil {
		return false, fmt.Errorf("failed to parse Talos version %q: %w", talosVersion, err)
	}

	// If the update is supported not because the machine is booted with UKI, but because its version is >= 1.12,
	// we need to additionally check that GrubUseUKICmdline is set to true if the machine is not in maintenance mode.
	//
	// This can happen with the machines which were allocated to a cluster that was created with an older version of Talos,
	// and their .machine.install.extraKernelArgs field was populated via a ConfigPatch.
	if parsedTalosVersion.Major == 1 && parsedTalosVersion.Minor < 12 {
		return false, nil
	}

	if getClusterMachineConfig == nil {
		return true, nil
	}

	clusterMachineConfig, err := getClusterMachineConfig()
	if err != nil && !state.IsNotFoundError(err) {
		return false, fmt.Errorf("failed to get cluster machine config: %w", err)
	}

	if clusterMachineConfig == nil {
		return true, nil
	}

	return clusterMachineConfig.TypedSpec().Value.GrubUseUkiCmdline, nil
}

func Calculate(machineStatus *omni.MachineStatus, kernelArgs *omni.KernelArgs) (args []string, initialized bool, err error) {
	if !machineStatus.TypedSpec().Value.SchematicReady() {
		return nil, false, nil
	}

	if _, initialized = machineStatus.Metadata().Annotations().Get(omni.KernelArgsInitialized); !initialized {
		return nil, false, nil
	}

	var extraArgs []string

	if kernelArgs != nil {
		extraArgs = kernelArgs.TypedSpec().Value.Args
	}

	baseArgs := xslices.Filter(machineStatus.TypedSpec().Value.Schematic.KernelArgs, isProtected)

	currentArgs := machineStatus.TypedSpec().Value.Schematic.KernelArgs
	calculatedArgs := slices.Concat(baseArgs, extraArgs)

	if equal(currentArgs, calculatedArgs) {
		return currentArgs, true, nil
	}

	return calculatedArgs, true, nil
}

// equal checks whether the given kernel args are logically equal.
//
// It does the comparison in a defensive way to prevent unwanted upgrades:
//   - protected args (siderolink, events sink, etc.) are compared as an unordered set (as their order doesn't matter in Talos)
//   - user (extra) args are compared as an ordered list (kernel args order actually matters)
func equal(a, b []string) bool {
	aProtected := FilterProtected(a)
	bProtected := FilterProtected(b)

	slices.Sort(aProtected)
	slices.Sort(bProtected)

	if !slices.Equal(aProtected, bProtected) {
		return false
	}

	return slices.Equal(FilterExtras(a), FilterExtras(b))
}

// FilterProtected filters out the "extra args" from the provided kernel args, leaving only the protected kernel arguments that cannot be modified.
func FilterProtected(args []string) []string {
	return xslices.Filter(args, isProtected)
}

// FilterExtras filters out the protected kernel arguments from the provided kernel args, leaving only the "extra args" that can be modified.
func FilterExtras(args []string) []string {
	return xslices.Filter(args, func(value string) bool {
		return !isProtected(value)
	})
}

func isProtected(arg string) bool {
	for _, prefix := range []string{
		constants.KernelParamSideroLink, constants.KernelParamEventsSink, constants.KernelParamLoggingKernel,
		constants.KernelParamConfig, constants.KernelParamConfigEarly, constants.KernelParamConfigInline,
	} {
		if strings.HasPrefix(arg, prefix+"=") {
			return true
		}
	}

	return false
}

// GetUncached reads the KernelArgs resource with the given ID, bypassing the resource cache.
//
// We need this to avoid stale reads of the KernelArgs resource: there can be cases where the omni.KernelArgsInitialized annotation is present in the MachineStatus,
// but the KernelArgs resource is not yet visible due to the resource cache, which can cause unwanted Talos upgrades through a schematic id update.
func GetUncached(ctx context.Context, r controller.Reader, id resource.ID) (*omni.KernelArgs, error) {
	uncachedReader, ok := r.(controller.UncachedReader)
	if !ok {
		return nil, fmt.Errorf("reader does not support uncached reads")
	}

	kernelArgs, err := uncachedReader.GetUncached(ctx, omni.NewKernelArgs(id).Metadata())
	if err != nil {
		return nil, fmt.Errorf("error getting extra kernel args configuration: %w", err)
	}

	kernelArgsTyped, ok := kernelArgs.(*omni.KernelArgs)
	if !ok {
		return nil, fmt.Errorf("unexpected resource type: %T", kernelArgs)
	}

	return kernelArgsTyped, nil
}