// Package cri inspects the container runtime configuration on the node.
package cri

import (
	"errors"
	"fmt"
	"os"
	"sort"

	"github.com/pelletier/go-toml/v2"
)

// ErrConfigNotFound is returned when the containerd config file does not
// exist.
var ErrConfigNotFound = errors.New("containerd config not found")

// Containerd holds the CRI runtime handlers configured in containerd.
type Containerd struct {
	path     string
	handlers map[string]struct{}
}

// Load parses the containerd config at the given path and collects the CRI
// runtime handler names from
// [plugins."io.containerd.grpc.v1.cri".containerd.runtimes.<name>] (and the
// legacy [plugins.cri.containerd.runtimes.<name>] spelling).
func Load(path string) (*Containerd, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("%w: %s", ErrConfigNotFound, path)
		}
		return nil, err
	}
	var tree map[string]interface{}
	if err := toml.Unmarshal(data, &tree); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	c := &Containerd{path: path, handlers: map[string]struct{}{}}
	c.collectHandlers(tree)
	return c, nil
}

func (c *Containerd) collectHandlers(tree map[string]interface{}) {
	plugins, _ := tree["plugins"].(map[string]interface{})
	for _, criName := range []string{"io.containerd.grpc.v1.cri", "cri"} {
		criSection, _ := plugins[criName].(map[string]interface{})
		containerdSection, _ := criSection["containerd"].(map[string]interface{})
		runtimes, _ := containerdSection["runtimes"].(map[string]interface{})
		for handler := range runtimes {
			c.handlers[handler] = struct{}{}
		}
	}
}

// HandlerNames returns the configured runtime handler names, sorted.
func (c *Containerd) HandlerNames() []string {
	names := make([]string, 0, len(c.handlers))
	for h := range c.handlers {
		names = append(names, h)
	}
	sort.Strings(names)
	return names
}

// HasHandler reports whether the named runtime handler is configured.
func (c *Containerd) HasHandler(name string) bool {
	_, ok := c.handlers[name]
	return ok
}