package idpsync

import (
	"context"
	"encoding/json"
	"fmt"

	"github.com/golang-jwt/jwt/v4"
	"github.com/google/uuid"
	"golang.org/x/xerrors"

	"cdr.dev/slog"
	"github.com/coder/coder/v2/coderd/database"
	"github.com/coder/coder/v2/coderd/database/db2sdk"
	"github.com/coder/coder/v2/coderd/database/dbauthz"
	"github.com/coder/coder/v2/coderd/runtimeconfig"
	"github.com/coder/coder/v2/coderd/util/ptr"
	"github.com/coder/coder/v2/coderd/util/slice"
	"github.com/coder/coder/v2/codersdk"
)

type GroupParams struct {
	// SyncEntitled if false will skip syncing the user's groups
	SyncEntitled bool
	MergedClaims jwt.MapClaims
}

func (AGPLIDPSync) GroupSyncEntitled() bool {
	// AGPL does not support syncing groups.
	return false
}

func (s AGPLIDPSync) UpdateGroupSyncSettings(ctx context.Context, orgID uuid.UUID, db database.Store, settings GroupSyncSettings) error {
	orgResolver := s.Manager.OrganizationResolver(db, orgID)
	err := s.SyncSettings.Group.SetRuntimeValue(ctx, orgResolver, &settings)
	if err != nil {
		return xerrors.Errorf("update group sync settings: %w", err)
	}

	return nil
}

func (s AGPLIDPSync) GroupSyncSettings(ctx context.Context, orgID uuid.UUID, db database.Store) (*GroupSyncSettings, error) {
	orgResolver := s.Manager.OrganizationResolver(db, orgID)
	settings, err := s.SyncSettings.Group.Resolve(ctx, orgResolver)
	if err != nil {
		if !xerrors.Is(err, runtimeconfig.ErrEntryNotFound) {
			return nil, xerrors.Errorf("resolve group sync settings: %w", err)
		}

		// Default to not being configured
		settings = &GroupSyncSettings{}

		// Check for legacy settings if the default org.
		if s.DeploymentSyncSettings.Legacy.GroupField != "" {
			defaultOrganization, err := db.GetDefaultOrganization(ctx)
			if err != nil {
				return nil, xerrors.Errorf("get default organization: %w", err)
			}
			if defaultOrganization.ID == orgID {
				settings = ptr.Ref(GroupSyncSettings(codersdk.GroupSyncSettings{
					Field:             s.Legacy.GroupField,
					LegacyNameMapping: s.Legacy.GroupMapping,
					RegexFilter:       s.Legacy.GroupFilter,
					AutoCreateMissing: s.Legacy.CreateMissingGroups,
				}))
			}
		}
	}

	return settings, nil
}

func (s AGPLIDPSync) ParseGroupClaims(_ context.Context, _ jwt.MapClaims) (GroupParams, *HTTPError) {
	return GroupParams{
		SyncEntitled: s.GroupSyncEntitled(),
	}, nil
}

func (s AGPLIDPSync) SyncGroups(ctx context.Context, db database.Store, user database.User, params GroupParams) error {
	// Nothing happens if sync is not enabled
	if !params.SyncEntitled {
		return nil
	}

	// nolint:gocritic // all syncing is done as a system user
	ctx = dbauthz.AsSystemRestricted(ctx)

	err := db.InTx(func(tx database.Store) error {
		userGroups, err := tx.GetGroups(ctx, database.GetGroupsParams{
			HasMemberID: user.ID,
		})
		if err != nil {
			return xerrors.Errorf("get user groups: %w", err)
		}

		// Figure out which organizations the user is a member of.
		// The "Everyone" group is always included, so we can infer organization
		// membership via the groups the user is in.
		userOrgs := make(map[uuid.UUID][]database.GetGroupsRow)
		for _, g := range userGroups {
			g := g
			userOrgs[g.Group.OrganizationID] = append(userOrgs[g.Group.OrganizationID], g)
		}

		// For each org, we need to fetch the sync settings
		// This loop also handles any legacy settings for the default
		// organization.
		orgSettings := make(map[uuid.UUID]GroupSyncSettings)
		for orgID := range userOrgs {
			settings, err := s.GroupSyncSettings(ctx, orgID, tx)
			if err != nil {
				// TODO: This error is currently silent to org admins.
				// We need to come up with a way to notify the org admin of this
				// error.
				s.Logger.Error(ctx, "failed to get group sync settings",
					slog.F("organization_id", orgID),
					slog.Error(err),
				)
				settings = &GroupSyncSettings{}
			}
			orgSettings[orgID] = *settings
		}

		// groupIDsToAdd & groupIDsToRemove are the final group differences
		// needed to be applied to user. The loop below will iterate over all
		// organizations the user is in, and determine the diffs.
		// The diffs are applied as a batch sql query, rather than each
		// organization having to execute a query.
		groupIDsToAdd := make([]uuid.UUID, 0)
		groupIDsToRemove := make([]uuid.UUID, 0)
		// For each org, determine which groups the user should land in
		for orgID, settings := range orgSettings {
			if settings.Field == "" {
				// No group sync enabled for this org, so do nothing.
				// The user can remain in their groups for this org.
				continue
			}

			// expectedGroups is the set of groups the IDP expects the
			// user to be a member of.
			expectedGroups, err := settings.ParseClaims(orgID, params.MergedClaims)
			if err != nil {
				s.Logger.Debug(ctx, "failed to parse claims for groups",
					slog.F("organization_field", s.GroupField),
					slog.F("organization_id", orgID),
					slog.Error(err),
				)
				// Unsure where to raise this error on the UI or database.
				// TODO: This error prevents group sync, but we have no way
				// to raise this to an org admin. Come up with a solution to
				// notify the admin and user of this issue.
				continue
			}
			// Everyone group is always implied, so include it.
			expectedGroups = append(expectedGroups, ExpectedGroup{
				OrganizationID: orgID,
				GroupID:        &orgID,
			})

			// Now we know what groups the user should be in for a given org,
			// determine if we have to do any group updates to sync the user's
			// state.
			existingGroups := userOrgs[orgID]
			existingGroupsTyped := db2sdk.List(existingGroups, func(f database.GetGroupsRow) ExpectedGroup {
				return ExpectedGroup{
					OrganizationID: orgID,
					GroupID:        &f.Group.ID,
					GroupName:      &f.Group.Name,
				}
			})

			add, remove := slice.SymmetricDifferenceFunc(existingGroupsTyped, expectedGroups, func(a, b ExpectedGroup) bool {
				return a.Equal(b)
			})

			for _, r := range remove {
				if r.GroupID == nil {
					// This should never happen. All group removals come from the
					// existing set, which come from the db. All groups from the
					// database have IDs. This code is purely defensive.
					detail := "user:" + user.Username
					if r.GroupName != nil {
						detail += fmt.Sprintf(" from group %s", *r.GroupName)
					}
					return xerrors.Errorf("removal group has nil ID, which should never happen: %s", detail)
				}
				groupIDsToRemove = append(groupIDsToRemove, *r.GroupID)
			}

			// HandleMissingGroups will add the new groups to the org if
			// the settings specify. It will convert all group names into uuids
			// for easier assignment.
			// TODO: This code should be batched at the end of the for loop.
			// Optimizing this is being pushed because if AutoCreate is disabled,
			// this code will only add cost on the first login for each user.
			// AutoCreate is usually disabled for large deployments.
			// For small deployments, this is less of a problem.
			assignGroups, err := settings.HandleMissingGroups(ctx, tx, orgID, add)
			if err != nil {
				return xerrors.Errorf("handle missing groups: %w", err)
			}

			groupIDsToAdd = append(groupIDsToAdd, assignGroups...)
		}

		// ApplyGroupDifference will take the total adds and removes, and apply
		// them.
		err = s.ApplyGroupDifference(ctx, tx, user, groupIDsToAdd, groupIDsToRemove)
		if err != nil {
			return xerrors.Errorf("apply group difference: %w", err)
		}

		return nil
	}, nil)
	if err != nil {
		return err
	}

	return nil
}

// ApplyGroupDifference will add and remove the user from the specified groups.
func (s AGPLIDPSync) ApplyGroupDifference(ctx context.Context, tx database.Store, user database.User, add []uuid.UUID, removeIDs []uuid.UUID) error {
	if len(removeIDs) > 0 {
		removedGroupIDs, err := tx.RemoveUserFromGroups(ctx, database.RemoveUserFromGroupsParams{
			UserID:   user.ID,
			GroupIds: removeIDs,
		})
		if err != nil {
			return xerrors.Errorf("remove user from %d groups: %w", len(removeIDs), err)
		}
		if len(removedGroupIDs) != len(removeIDs) {
			s.Logger.Debug(ctx, "user not removed from expected number of groups",
				slog.F("user_id", user.ID),
				slog.F("groups_removed_count", len(removedGroupIDs)),
				slog.F("expected_count", len(removeIDs)),
			)
		}
	}

	if len(add) > 0 {
		add = slice.Unique(add)
		// Defensive programming to only insert uniques.
		assignedGroupIDs, err := tx.InsertUserGroupsByID(ctx, database.InsertUserGroupsByIDParams{
			UserID:   user.ID,
			GroupIds: add,
		})
		if err != nil {
			return xerrors.Errorf("insert user into %d groups: %w", len(add), err)
		}
		if len(assignedGroupIDs) != len(add) {
			s.Logger.Debug(ctx, "user not assigned to expected number of groups",
				slog.F("user_id", user.ID),
				slog.F("groups_assigned_count", len(assignedGroupIDs)),
				slog.F("expected_count", len(add)),
			)
		}
	}

	return nil
}

type GroupSyncSettings codersdk.GroupSyncSettings

func (s *GroupSyncSettings) Set(v string) error {
	return json.Unmarshal([]byte(v), s)
}

func (s *GroupSyncSettings) String() string {
	return runtimeconfig.JSONString(s)
}

type ExpectedGroup struct {
	OrganizationID uuid.UUID
	GroupID        *uuid.UUID
	GroupName      *string
}

// Equal compares two ExpectedGroups. The org id must be the same.
// If the group ID is set, it will be compared and take priority, ignoring the
// name value. So 2 groups with the same ID but different names will be
// considered equal.
func (a ExpectedGroup) Equal(b ExpectedGroup) bool {
	// Must match
	if a.OrganizationID != b.OrganizationID {
		return false
	}
	// Only the name or the name needs to be checked, priority is given to the ID.
	if a.GroupID != nil && b.GroupID != nil {
		return *a.GroupID == *b.GroupID
	}
	if a.GroupName != nil && b.GroupName != nil {
		return *a.GroupName == *b.GroupName
	}

	// If everything is nil, it is equal. Although a bit pointless
	if a.GroupID == nil && b.GroupID == nil &&
		a.GroupName == nil && b.GroupName == nil {
		return true
	}
	return false
}

// ParseClaims will take the merged claims from the IDP and return the groups
// the user is expected to be a member of. The expected group can either be a
// name or an ID.
// It is unfortunate we cannot use exclusively names or exclusively IDs.
// When configuring though, if a group is mapped from "A" -> "UUID 1234", and
// the group "UUID 1234" is renamed, we want to maintain the mapping.
// We have to keep names because group sync supports syncing groups by name if
// the external IDP group name matches the Coder one.
func (s GroupSyncSettings) ParseClaims(orgID uuid.UUID, mergedClaims jwt.MapClaims) ([]ExpectedGroup, error) {
	groupsRaw, ok := mergedClaims[s.Field]
	if !ok {
		return []ExpectedGroup{}, nil
	}

	parsedGroups, err := ParseStringSliceClaim(groupsRaw)
	if err != nil {
		return nil, xerrors.Errorf("parse groups field, unexpected type %T: %w", groupsRaw, err)
	}

	groups := make([]ExpectedGroup, 0)
	for _, group := range parsedGroups {
		group := group

		// Legacy group mappings happen before the regex filter.
		mappedGroupName, ok := s.LegacyNameMapping[group]
		if ok {
			group = mappedGroupName
		}

		// Only allow through groups that pass the regex
		if s.RegexFilter != nil {
			if !s.RegexFilter.MatchString(group) {
				continue
			}
		}

		mappedGroupIDs, ok := s.Mapping[group]
		if ok {
			for _, gid := range mappedGroupIDs {
				gid := gid
				groups = append(groups, ExpectedGroup{OrganizationID: orgID, GroupID: &gid})
			}
			continue
		}

		groups = append(groups, ExpectedGroup{OrganizationID: orgID, GroupName: &group})
	}

	return groups, nil
}

// HandleMissingGroups ensures all ExpectedGroups convert to uuids.
// Groups can be referenced by name via legacy params or IDP group names.
// These group names are converted to IDs for easier assignment.
// Missing groups are created if AutoCreate is enabled.
// TODO: Batching this would be better, as this is 1 or 2 db calls per organization.
func (s GroupSyncSettings) HandleMissingGroups(ctx context.Context, tx database.Store, orgID uuid.UUID, add []ExpectedGroup) ([]uuid.UUID, error) {
	// All expected that are missing IDs means the group does not exist
	// in the database, or it is a legacy mapping, and we need to do a lookup.
	var missingGroups []string
	addIDs := make([]uuid.UUID, 0)

	for _, expected := range add {
		if expected.GroupID == nil && expected.GroupName != nil {
			missingGroups = append(missingGroups, *expected.GroupName)
		} else if expected.GroupID != nil {
			// Keep the IDs to sync the groups.
			addIDs = append(addIDs, *expected.GroupID)
		}
	}

	if s.AutoCreateMissing && len(missingGroups) > 0 {
		// Insert any missing groups. If the groups already exist, this is a noop.
		_, err := tx.InsertMissingGroups(ctx, database.InsertMissingGroupsParams{
			OrganizationID: orgID,
			Source:         database.GroupSourceOidc,
			GroupNames:     missingGroups,
		})
		if err != nil {
			return nil, xerrors.Errorf("insert missing groups: %w", err)
		}
	}

	// Fetch any missing groups by name. If they exist, their IDs will be
	// matched and returned.
	if len(missingGroups) > 0 {
		// Do name lookups for all groups that are missing IDs.
		newGroups, err := tx.GetGroups(ctx, database.GetGroupsParams{
			OrganizationID: orgID,
			HasMemberID:    uuid.UUID{},
			GroupNames:     missingGroups,
		})
		if err != nil {
			return nil, xerrors.Errorf("get groups by names: %w", err)
		}
		for _, g := range newGroups {
			addIDs = append(addIDs, g.Group.ID)
		}
	}

	return addIDs, nil
}

func ConvertAllowList(allowList []string) map[string]struct{} {
	allowMap := make(map[string]struct{}, len(allowList))
	for _, group := range allowList {
		allowMap[group] = struct{}{}
	}
	return allowMap
}