package vault

import (
	"fmt"
	"strings"

	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/hcl"
	"github.com/hashicorp/hcl/hcl/ast"
)

const (
	DenyCapability   = "deny"
	CreateCapability = "create"
	ReadCapability   = "read"
	UpdateCapability = "update"
	DeleteCapability = "delete"
	ListCapability   = "list"
	SudoCapability   = "sudo"
	RootCapability   = "root"

	// Backwards compatibility
	OldDenyPathPolicy  = "deny"
	OldReadPathPolicy  = "read"
	OldWritePathPolicy = "write"
	OldSudoPathPolicy  = "sudo"
)

const (
	DenyCapabilityInt uint32 = 1 << iota
	CreateCapabilityInt
	ReadCapabilityInt
	UpdateCapabilityInt
	DeleteCapabilityInt
	ListCapabilityInt
	SudoCapabilityInt
)

var (
	cap2Int = map[string]uint32{
		DenyCapability:   DenyCapabilityInt,
		CreateCapability: CreateCapabilityInt,
		ReadCapability:   ReadCapabilityInt,
		UpdateCapability: UpdateCapabilityInt,
		DeleteCapability: DeleteCapabilityInt,
		ListCapability:   ListCapabilityInt,
		SudoCapability:   SudoCapabilityInt,
	}
)

// Policy is used to represent the policy specified by
// an ACL configuration.
type Policy struct {
	Name  string              `hcl:"name"`
	Paths []*PathCapabilities `hcl:"-"`
	Raw   string
}

// PathCapabilities represents a policy for a path in the namespace.
type PathCapabilities struct {
	Prefix             string
	Policy             string
	Capabilities       []string
	CapabilitiesBitmap uint32 `hcl:"-"`
	Glob               bool
}

// Parse is used to parse the specified ACL rules into an
// intermediary set of policies, before being compiled into
// the ACL
func Parse(rules string) (*Policy, error) {
	// Parse the rules
	root, err := hcl.Parse(rules)
	if err != nil {
		return nil, fmt.Errorf("Failed to parse policy: %s", err)
	}

	// Top-level item should be the object list
	list, ok := root.Node.(*ast.ObjectList)
	if !ok {
		return nil, fmt.Errorf("Failed to parse policy: does not contain a root object")
	}

	// Check for invalid top-level keys
	valid := []string{
		"name",
		"path",
	}
	if err := checkHCLKeys(list, valid); err != nil {
		return nil, fmt.Errorf("Failed to parse policy: %s", err)
	}

	// Create the initial policy and store the raw text of the rules
	var p Policy
	p.Raw = rules
	if err := hcl.DecodeObject(&p, list); err != nil {
		return nil, fmt.Errorf("Failed to parse policy: %s", err)
	}

	if o := list.Filter("path"); len(o.Items) > 0 {
		if err := parsePaths(&p, o); err != nil {
			return nil, fmt.Errorf("Failed to parse policy: %s", err)
		}
	}

	return &p, nil
}

func parsePaths(result *Policy, list *ast.ObjectList) error {
	paths := make([]*PathCapabilities, 0, len(list.Items))
	for _, item := range list.Items {
		key := "path"
		if len(item.Keys) > 0 {
			key = item.Keys[0].Token.Value().(string)
		}

		valid := []string{
			"policy",
			"capabilities",
		}
		if err := checkHCLKeys(item.Val, valid); err != nil {
			return multierror.Prefix(err, fmt.Sprintf("path %q:", key))
		}

		var pc PathCapabilities
		pc.Prefix = key
		if err := hcl.DecodeObject(&pc, item.Val); err != nil {
			return multierror.Prefix(err, fmt.Sprintf("path %q:", key))
		}

		// Strip a leading '/' as paths in Vault start after the / in the API path
		if len(pc.Prefix) > 0 && pc.Prefix[0] == '/' {
			pc.Prefix = pc.Prefix[1:]
		}

		// Strip the glob character if found
		if strings.HasSuffix(pc.Prefix, "*") {
			pc.Prefix = strings.TrimSuffix(pc.Prefix, "*")
			pc.Glob = true
		}

		// Map old-style policies into capabilities
		if len(pc.Policy) > 0 {
			switch pc.Policy {
			case OldDenyPathPolicy:
				pc.Capabilities = []string{DenyCapability}
			case OldReadPathPolicy:
				pc.Capabilities = append(pc.Capabilities, []string{ReadCapability, ListCapability}...)
			case OldWritePathPolicy:
				pc.Capabilities = append(pc.Capabilities, []string{CreateCapability, ReadCapability, UpdateCapability, DeleteCapability, ListCapability}...)
			case OldSudoPathPolicy:
				pc.Capabilities = append(pc.Capabilities, []string{CreateCapability, ReadCapability, UpdateCapability, DeleteCapability, ListCapability, SudoCapability}...)
			default:
				return fmt.Errorf("path %q: invalid policy '%s'", key, pc.Policy)
			}
		}

		// Initialize the map
		pc.CapabilitiesBitmap = 0
		for _, cap := range pc.Capabilities {
			switch cap {
			// If it's deny, don't include any other capability
			case DenyCapability:
				pc.Capabilities = []string{DenyCapability}
				pc.CapabilitiesBitmap = DenyCapabilityInt
				goto PathFinished
			case CreateCapability, ReadCapability, UpdateCapability, DeleteCapability, ListCapability, SudoCapability:
				pc.CapabilitiesBitmap |= cap2Int[cap]
			default:
				return fmt.Errorf("path %q: invalid capability '%s'", key, cap)
			}
		}

	PathFinished:

		paths = append(paths, &pc)
	}

	result.Paths = paths
	return nil
}

func checkHCLKeys(node ast.Node, valid []string) error {
	var list *ast.ObjectList
	switch n := node.(type) {
	case *ast.ObjectList:
		list = n
	case *ast.ObjectType:
		list = n.List
	default:
		return fmt.Errorf("cannot check HCL keys of type %T", n)
	}

	validMap := make(map[string]struct{}, len(valid))
	for _, v := range valid {
		validMap[v] = struct{}{}
	}

	var result error
	for _, item := range list.Items {
		key := item.Keys[0].Token.Value().(string)
		if _, ok := validMap[key]; !ok {
			result = multierror.Append(result, fmt.Errorf(
				"invalid key '%s' on line %d", key, item.Assign.Line))
		}
	}

	return result
}