package rbac

import (
	"sort"
	"strings"

	"github.com/google/uuid"
	"github.com/open-policy-agent/opa/ast"

	"golang.org/x/xerrors"
)

const (
	owner         string = "owner"
	member        string = "member"
	templateAdmin string = "template-admin"
	userAdmin     string = "user-admin"
	auditor       string = "auditor"

	orgAdmin  string = "organization-admin"
	orgMember string = "organization-member"
)

func init() {
	// Always load defaults
	ReloadBuiltinRoles(nil)
}

// RoleNames is a list of user assignable role names. The role names must be
// in the builtInRoles map. Any non-user assignable roles will generate an
// error on Expand.
type RoleNames []string

func (names RoleNames) Expand() ([]Role, error) {
	return rolesByNames(names)
}

func (names RoleNames) Names() []string {
	return names
}

// The functions below ONLY need to exist for roles that are "defaulted" in some way.
// Any other roles (like auditor), can be listed and let the user select/assigned.
// Once we have a database implementation, the "default" roles can be defined on the
// site and orgs, and these functions can be removed.

func RoleOwner() string {
	return roleName(owner, "")
}

func RoleTemplateAdmin() string {
	return roleName(templateAdmin, "")
}

func RoleUserAdmin() string {
	return roleName(userAdmin, "")
}

func RoleMember() string {
	return roleName(member, "")
}

func RoleOrgAdmin(organizationID uuid.UUID) string {
	return roleName(orgAdmin, organizationID.String())
}

func RoleOrgMember(organizationID uuid.UUID) string {
	return roleName(orgMember, organizationID.String())
}

func allPermsExcept(excepts ...Object) []Permission {
	resources := AllResources()
	var perms []Permission
	skip := make(map[string]bool)
	for _, e := range excepts {
		skip[e.Type] = true
	}

	for _, r := range resources {
		// Exceptions
		if skip[r.Type] {
			continue
		}
		// This should always be skipped.
		if r.Type == ResourceWildcard.Type {
			continue
		}
		// Owners can do everything else
		perms = append(perms, Permission{
			Negate:       false,
			ResourceType: r.Type,
			Action:       WildcardSymbol,
		})
	}
	return perms
}

// builtInRoles are just a hard coded set for now. Ideally we store these in
// the database. Right now they are functions because the org id should scope
// certain roles. When we store them in the database, each organization should
// create the roles that are assignable in the org. This isn't a hard problem to solve,
// it's just easier as a function right now.
//
// This map will be replaced by database storage defined by this ticket.
// https://github.com/coder/coder/issues/1194
var builtInRoles map[string]func(orgID string) Role

type RoleOptions struct {
	NoOwnerWorkspaceExec bool
}

// ReloadBuiltinRoles loads the static roles into the builtInRoles map.
// This can be called again with a different config to change the behavior.
//
// TODO: @emyrk This would be great if it was instanced to a coderd rather
// than a global. But that is a much larger refactor right now.
// Essentially we did not foresee different deployments needing slightly
// different role permissions.
func ReloadBuiltinRoles(opts *RoleOptions) {
	if opts == nil {
		opts = &RoleOptions{}
	}

	ownerAndAdminExceptions := []Object{ResourceWorkspaceLocked}
	if opts.NoOwnerWorkspaceExec {
		ownerAndAdminExceptions = append(ownerAndAdminExceptions,
			ResourceWorkspaceExecution,
			ResourceWorkspaceApplicationConnect,
		)
	}

	// Static roles that never change should be allocated in a closure.
	// This is to ensure these data structures are only allocated once and not
	// on every authorize call. 'withCachedRegoValue' can be used as well to
	// preallocate the rego value that is used by the rego eval engine.
	ownerRole := Role{
		Name:        owner,
		DisplayName: "Owner",
		Site:        allPermsExcept(ownerAndAdminExceptions...),
		Org:         map[string][]Permission{},
		User:        []Permission{},
	}.withCachedRegoValue()

	memberRole := Role{
		Name:        member,
		DisplayName: "",
		Site: Permissions(map[string][]Action{
			// All users can read all other users and know they exist.
			ResourceUser.Type:           {ActionRead},
			ResourceRoleAssignment.Type: {ActionRead},
			// All users can see the provisioner daemons.
			ResourceProvisionerDaemon.Type: {ActionRead},
		}),
		Org:  map[string][]Permission{},
		User: allPermsExcept(ResourceWorkspaceLocked),
	}.withCachedRegoValue()

	auditorRole := Role{
		Name:        auditor,
		DisplayName: "Auditor",
		Site: Permissions(map[string][]Action{
			// Should be able to read all template details, even in orgs they
			// are not in.
			ResourceTemplate.Type: {ActionRead},
			ResourceAuditLog.Type: {ActionRead},
		}),
		Org:  map[string][]Permission{},
		User: []Permission{},
	}.withCachedRegoValue()

	templateAdminRole := Role{
		Name:        templateAdmin,
		DisplayName: "Template Admin",
		Site: Permissions(map[string][]Action{
			ResourceTemplate.Type: {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			// CRUD all files, even those they did not upload.
			ResourceFile.Type:      {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			ResourceWorkspace.Type: {ActionRead},
			// CRUD to provisioner daemons for now.
			ResourceProvisionerDaemon.Type: {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			// Needs to read all organizations since
			ResourceOrganization.Type: {ActionRead},
		}),
		Org:  map[string][]Permission{},
		User: []Permission{},
	}.withCachedRegoValue()

	userAdminRole := Role{
		Name:        userAdmin,
		DisplayName: "User Admin",
		Site: Permissions(map[string][]Action{
			ResourceRoleAssignment.Type: {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			ResourceUser.Type:           {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			// Full perms to manage org members
			ResourceOrganizationMember.Type: {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
			ResourceGroup.Type:              {ActionCreate, ActionRead, ActionUpdate, ActionDelete},
		}),
		Org:  map[string][]Permission{},
		User: []Permission{},
	}.withCachedRegoValue()

	builtInRoles = map[string]func(orgID string) Role{
		// admin grants all actions to all resources.
		owner: func(_ string) Role {
			return ownerRole
		},

		// member grants all actions to all resources owned by the user
		member: func(_ string) Role {
			return memberRole
		},

		// auditor provides all permissions required to effectively read and understand
		// audit log events.
		// TODO: Finish the auditor as we add resources.
		auditor: func(_ string) Role {
			return auditorRole
		},

		templateAdmin: func(_ string) Role {
			return templateAdminRole
		},

		userAdmin: func(_ string) Role {
			return userAdminRole
		},

		// orgAdmin returns a role with all actions allows in a given
		// organization scope.
		orgAdmin: func(organizationID string) Role {
			return Role{
				Name:        roleName(orgAdmin, organizationID),
				DisplayName: "Organization Admin",
				Site:        []Permission{},
				Org: map[string][]Permission{
					// Org admins should not have workspace exec perms.
					organizationID: allPermsExcept(ResourceWorkspaceExecution, ResourceWorkspaceLocked),
				},
				User: []Permission{},
			}
		},

		// orgMember has an empty set of permissions, this just implies their membership
		// in an organization.
		orgMember: func(organizationID string) Role {
			return Role{
				Name:        roleName(orgMember, organizationID),
				DisplayName: "",
				Site:        []Permission{},
				Org: map[string][]Permission{
					organizationID: {
						{
							// All org members can read the other members in their org.
							ResourceType: ResourceOrganizationMember.Type,
							Action:       ActionRead,
						},
						{
							// All org members can read the organization
							ResourceType: ResourceOrganization.Type,
							Action:       ActionRead,
						},
						{
							// Can read available roles.
							ResourceType: ResourceOrgRoleAssignment.Type,
							Action:       ActionRead,
						},
						{
							ResourceType: ResourceGroup.Type,
							Action:       ActionRead,
						},
					},
				},
				User: []Permission{},
			}
		},
	}
}

// assignRoles is a map of roles that can be assigned if a user has a given
// role.
// The first key is the actor role, the second is the roles they can assign.
//
//	map[actor_role][assign_role]<can_assign>
var assignRoles = map[string]map[string]bool{
	"system": {
		owner:     true,
		member:    true,
		orgAdmin:  true,
		orgMember: true,
	},
	owner: {
		owner:         true,
		auditor:       true,
		member:        true,
		orgAdmin:      true,
		orgMember:     true,
		templateAdmin: true,
		userAdmin:     true,
	},
	userAdmin: {
		member:    true,
		orgMember: true,
	},
	orgAdmin: {
		orgAdmin:  true,
		orgMember: true,
	},
}

// ExpandableRoles is any type that can be expanded into a []Role. This is implemented
// as an interface so we can have RoleNames for user defined roles, and implement
// custom ExpandableRoles for system type users (eg autostart/autostop system role).
// We want a clear divide between the two types of roles so users have no codepath
// to interact or assign system roles.
//
// Note: We may also want to do the same thing with scopes to allow custom scope
// support unavailable to the user. Eg: Scope to a single resource.
type ExpandableRoles interface {
	Expand() ([]Role, error)
	// Names is for logging and tracing purposes, we want to know the human
	// names of the expanded roles.
	Names() []string
}

// Permission is the format passed into the rego.
type Permission struct {
	// Negate makes this a negative permission
	Negate       bool   `json:"negate"`
	ResourceType string `json:"resource_type"`
	Action       Action `json:"action"`
}

// Role is a set of permissions at multiple levels:
// - Site level permissions apply EVERYWHERE
// - Org level permissions apply to EVERYTHING in a given ORG
// - User level permissions are the lowest
// This is the type passed into the rego as a json payload.
// Users of this package should instead **only** use the role names, and
// this package will expand the role names into their json payloads.
type Role struct {
	Name string `json:"name"`
	// DisplayName is used for UI purposes. If the role has no display name,
	// that means the UI should never display it.
	DisplayName string       `json:"display_name"`
	Site        []Permission `json:"site"`
	// Org is a map of orgid to permissions. We represent orgid as a string.
	// We scope the organizations in the role so we can easily combine all the
	// roles.
	Org  map[string][]Permission `json:"org"`
	User []Permission            `json:"user"`

	// cachedRegoValue can be used to cache the rego value for this role.
	// This is helpful for static roles that never change.
	cachedRegoValue ast.Value
}

type Roles []Role

func (roles Roles) Expand() ([]Role, error) {
	return roles, nil
}

func (roles Roles) Names() []string {
	names := make([]string, 0, len(roles))
	for _, r := range roles {
		return append(names, r.Name)
	}
	return names
}

// CanAssignRole is a helper function that returns true if the user can assign
// the specified role. This also can be used for removing a role.
// This is a simple implementation for now.
func CanAssignRole(expandable ExpandableRoles, assignedRole string) bool {
	// For CanAssignRole, we only care about the names of the roles.
	roles := expandable.Names()

	assigned, assignedOrg, err := roleSplit(assignedRole)
	if err != nil {
		return false
	}

	for _, longRole := range roles {
		role, orgID, err := roleSplit(longRole)
		if err != nil {
			continue
		}

		if orgID != "" && orgID != assignedOrg {
			// Org roles only apply to the org they are assigned to.
			continue
		}

		allowed, ok := assignRoles[role]
		if !ok {
			continue
		}

		if allowed[assigned] {
			return true
		}
	}
	return false
}

// RoleByName returns the permissions associated with a given role name.
// This allows just the role names to be stored and expanded when required.
//
// This function is exported so that the Display name can be returned to the
// api. We should maybe make an exported function that returns just the
// human-readable content of the Role struct (name + display name).
func RoleByName(name string) (Role, error) {
	roleName, orgID, err := roleSplit(name)
	if err != nil {
		return Role{}, xerrors.Errorf("parse role name: %w", err)
	}

	roleFunc, ok := builtInRoles[roleName]
	if !ok {
		// No role found
		return Role{}, xerrors.Errorf("role %q not found", roleName)
	}

	// Ensure all org roles are properly scoped a non-empty organization id.
	// This is just some defensive programming.
	role := roleFunc(orgID)
	if len(role.Org) > 0 && orgID == "" {
		return Role{}, xerrors.Errorf("expect a org id for role %q", roleName)
	}

	return role, nil
}

func rolesByNames(roleNames []string) ([]Role, error) {
	roles := make([]Role, 0, len(roleNames))
	for _, n := range roleNames {
		r, err := RoleByName(n)
		if err != nil {
			return nil, xerrors.Errorf("get role permissions: %w", err)
		}
		roles = append(roles, r)
	}
	return roles, nil
}

func IsOrgRole(roleName string) (string, bool) {
	_, orgID, err := roleSplit(roleName)
	if err == nil && orgID != "" {
		return orgID, true
	}
	return "", false
}

// OrganizationRoles lists all roles that can be applied to an organization user
// in the given organization. This is the list of available roles,
// and specific to an organization.
//
// This should be a list in a database, but until then we build
// the list from the builtins.
func OrganizationRoles(organizationID uuid.UUID) []Role {
	var roles []Role
	for _, roleF := range builtInRoles {
		role := roleF(organizationID.String())
		_, scope, err := roleSplit(role.Name)
		if err != nil {
			// This should never happen
			continue
		}
		if scope == organizationID.String() {
			roles = append(roles, role)
		}
	}
	return roles
}

// SiteRoles lists all roles that can be applied to a user.
// This is the list of available roles, and not specific to a user
//
// This should be a list in a database, but until then we build
// the list from the builtins.
func SiteRoles() []Role {
	var roles []Role
	for _, roleF := range builtInRoles {
		role := roleF("random")
		_, scope, err := roleSplit(role.Name)
		if err != nil {
			// This should never happen
			continue
		}
		if scope == "" {
			roles = append(roles, role)
		}
	}
	return roles
}

// ChangeRoleSet is a helper function that finds the difference of 2 sets of
// roles. When setting a user's new roles, it is equivalent to adding and
// removing roles. This set determines the changes, so that the appropriate
// RBAC checks can be applied using "ActionCreate" and "ActionDelete" for
// "added" and "removed" roles respectively.
func ChangeRoleSet(from []string, to []string) (added []string, removed []string) {
	has := make(map[string]struct{})
	for _, exists := range from {
		has[exists] = struct{}{}
	}

	for _, roleName := range to {
		// If the user already has the role assigned, we don't need to check the permission
		// to reassign it. Only run permission checks on the difference in the set of
		// roles.
		if _, ok := has[roleName]; ok {
			delete(has, roleName)
			continue
		}

		added = append(added, roleName)
	}

	// Remaining roles are the ones removed/deleted.
	for roleName := range has {
		removed = append(removed, roleName)
	}

	return added, removed
}

// roleName is a quick helper function to return
//
//	role_name:scopeID
//
// If no scopeID is required, only 'role_name' is returned
func roleName(name string, orgID string) string {
	if orgID == "" {
		return name
	}
	return name + ":" + orgID
}

func roleSplit(role string) (name string, orgID string, err error) {
	arr := strings.Split(role, ":")
	if len(arr) > 2 {
		return "", "", xerrors.Errorf("too many colons in role name")
	}

	if arr[0] == "" {
		return "", "", xerrors.Errorf("role cannot be the empty string")
	}

	if len(arr) == 2 {
		return arr[0], arr[1], nil
	}
	return arr[0], "", nil
}

// Permissions is just a helper function to make building roles that list out resources
// and actions a bit easier.
func Permissions(perms map[string][]Action) []Permission {
	list := make([]Permission, 0, len(perms))
	for k, actions := range perms {
		for _, act := range actions {
			act := act
			list = append(list, Permission{
				Negate:       false,
				ResourceType: k,
				Action:       act,
			})
		}
	}
	// Deterministic ordering of permissions
	sort.Slice(list, func(i, j int) bool {
		return list[i].ResourceType < list[j].ResourceType
	})
	return list
}