package vault

import (
	"encoding/json"
	"errors"
	"fmt"
	"path/filepath"
	"sort"
	"strings"
	"sync"

	"github.com/hashicorp/vault/helper/builtinplugins"
	"github.com/hashicorp/vault/helper/jsonutil"
	"github.com/hashicorp/vault/helper/pluginutil"
	"github.com/hashicorp/vault/logical"
)

var (
	pluginCatalogPrefix = "plugin-catalog/"
)

// PluginCatalog keeps a record of plugins known to vault. External plugins need
// to be registered to the catalog before they can be used in backends. Builtin
// plugins are automatically detected and included in the catalog.
type PluginCatalog struct {
	catalogView  *BarrierView
	directory    string
	vaultCommand string
	vaultSHA256  []byte

	lock sync.RWMutex
}

func (c *Core) setupPluginCatalog() error {
	c.pluginCatalog = &PluginCatalog{
		catalogView:  c.systemBarrierView.SubView(pluginCatalogPrefix),
		directory:    c.pluginDirectory,
		vaultCommand: c.vaultBinaryLocation,
		vaultSHA256:  c.vaultBinarySHA256,
	}

	return nil
}

// Get retrieves a plugin with the specified name from the catalog. It first
// looks for external plugins with this name and then looks for builtin plugins.
// It returns a PluginRunner or an error if no plugin was found.
func (c *PluginCatalog) Get(name string) (*pluginutil.PluginRunner, error) {
	c.lock.RLock()
	defer c.lock.RUnlock()

	// Look for external plugins in the barrier
	out, err := c.catalogView.Get(name)
	if err != nil {
		return nil, fmt.Errorf("failed to retrieve plugin \"%s\": %v", name, err)
	}
	if out != nil {
		entry := new(pluginutil.PluginRunner)
		if err := jsonutil.DecodeJSON(out.Value, entry); err != nil {
			return nil, fmt.Errorf("failed to decode plugin entry: %v", err)
		}

		return entry, nil
	}

	// Look for builtin plugins
	if _, ok := builtinplugins.BuiltinPlugins.Get(name); !ok {
		return nil, fmt.Errorf("no plugin found with name: %s", name)
	}

	return &pluginutil.PluginRunner{
		Name:    name,
		Command: c.vaultCommand,
		Args:    []string{"plugin-exec", name},
		Sha256:  c.vaultSHA256,
		Builtin: true,
	}, nil
}

// Set registers a new external plugin with the catalog, or updates an existing
// external plugin. It takes the name, command and SHA256 of the plugin.
func (c *PluginCatalog) Set(name, command string, sha256 []byte) error {
	c.lock.Lock()
	defer c.lock.Unlock()

	parts := strings.Split(command, " ")
	command = parts[0]
	args := parts[1:]

	command = filepath.Join(c.directory, command)

	// Best effort check to make sure the command isn't breaking out of the
	// configured plugin directory.
	sym, err := filepath.EvalSymlinks(command)
	if err != nil {
		return fmt.Errorf("error while validating the command path: %v", err)
	}
	symAbs, err := filepath.Abs(filepath.Dir(sym))
	if err != nil {
		return fmt.Errorf("error while validating the command path: %v", err)
	}

	if symAbs != c.directory {
		return errors.New("can not execute files outside of configured plugin directory")
	}

	entry := &pluginutil.PluginRunner{
		Name:    name,
		Command: command,
		Args:    args,
		Sha256:  sha256,
		Builtin: false,
	}

	buf, err := json.Marshal(entry)
	if err != nil {
		return fmt.Errorf("failed to encode plugin entry: %v", err)
	}

	logicalEntry := logical.StorageEntry{
		Key:   name,
		Value: buf,
	}
	if err := c.catalogView.Put(&logicalEntry); err != nil {
		return fmt.Errorf("failed to persist plugin entry: %v", err)
	}
	return nil
}

// Delete is used to remove an external plugin from the catalog. Builtin plugins
// can not be deleted.
func (c *PluginCatalog) Delete(name string) error {
	c.lock.Lock()
	defer c.lock.Unlock()

	return c.catalogView.Delete(name)
}

// List returns a list of all the known plugin names. If an external and builtin
// plugin share the same name, only one instance of the name will be returned.
func (c *PluginCatalog) List() ([]string, error) {
	c.lock.RLock()
	defer c.lock.RUnlock()

	// Collect keys for external plugins in the barrier.
	keys, err := logical.CollectKeys(c.catalogView)
	if err != nil {
		return nil, err
	}

	// Get the keys for builtin plugins
	builtinKeys := builtinplugins.BuiltinPlugins.Keys()

	// Use a map to unique the two lists
	mapKeys := make(map[string]bool)

	for _, plugin := range keys {
		mapKeys[plugin] = true
	}

	for _, plugin := range builtinKeys {
		mapKeys[plugin] = true
	}

	retList := make([]string, len(mapKeys))
	i := 0
	for k := range mapKeys {
		retList[i] = k
		i++
	}
	// sort for consistent ordering of builtin pluings
	sort.Strings(retList)

	return retList, nil
}