// Package engine provides rule evaluation and execution
package engine

import (
	"context"
	"fmt"
	"time"

	"github.com/Grace-Solutions/OrchestrAD/internal/directory/ldap"
	"github.com/Grace-Solutions/OrchestrAD/internal/logging"
	"github.com/Grace-Solutions/OrchestrAD/internal/models"
	"github.com/Grace-Solutions/OrchestrAD/internal/types"
	ldapv3 "github.com/go-ldap/ldap/v3"
)

// Engine executes rules against Active Directory
type Engine struct {
	logger  *logging.Logger
	managed ManagedMemberStore
}

// NewEngine creates a new rule engine
func NewEngine(logger *logging.Logger) *Engine {
	return &Engine{logger: logger}
}

// SetManagedStore attaches the managed-membership store used by the ManagedAdd
// sync mode to remember which memberships this engine added. Optional; when
// unset, ManagedAdd never removes and FullSync is unaffected.
func (e *Engine) SetManagedStore(store ManagedMemberStore) {
	e.managed = store
}

// isSetAction reports whether an action operates on the whole matched set at
// once (rather than per matched object).
func isSetAction(actionType string) bool {
	return types.ActionType(actionType) == types.ActionSyncGroupMembership
}

// ExecutionResult contains the results of rule execution
type ExecutionResult struct {
	RuleID           string
	Status           types.RunStatus
	StartedAt        time.Time
	CompletedAt      time.Time
	Duration         time.Duration
	ObjectsMatched   int
	ObjectsProcessed int
	ActionsExecuted  int
	ActionsFailed    int
	Errors           []string
	ActionResults    []ActionResult
}

// ActionResult contains the result of a single action
type ActionResult struct {
	ActionID   string
	ActionType string
	ObjectDN   string
	Success    bool
	Error      string
	Duration   time.Duration
	Details    map[string]any
}

// actionOutcome is the internal outcome of a single action execution
type actionOutcome struct {
	ActionID   string
	ActionType string
	ObjectDN   string
	Success    bool
	Error      string
	Details    map[string]any
}

func (o *actionOutcome) fail(err error) {
	o.Success = false
	if err != nil {
		o.Error = err.Error()
	}
}

// PreviewResult contains a preview of what would be executed
type PreviewResult struct {
	RuleID          string
	MatchedObjects  []MatchedObject
	PlannedActions  []PlannedAction
	Warnings        []string
	GeneratedFilter string
}

// MatchedObject represents an AD object that matched rule conditions
type MatchedObject struct {
	DN string
	// CanonicalName is the operator-friendly name (domain.com/OU/CN), from the
	// directory's canonicalName attribute when present, else built from the DN.
	CanonicalName string
	ObjectType    string
	Attributes    map[string][]string
}

// PlannedAction represents an action that would be executed
type PlannedAction struct {
	ActionID    string
	ActionType  string
	TargetDN    string
	Description string
	IsChange    bool
}

// Preview generates a preview of rule execution without making changes
func (e *Engine) Preview(ctx context.Context, rule *models.Rule, conn *models.ADConnection, client *ldap.Client) (*PreviewResult, error) {
	e.logger.Info("RuleEngine", "Generating preview for rule '%s'", rule.Name)

	result := &PreviewResult{
		RuleID: rule.ID,
	}

	conditionGroups := buildConditionGroups(rule)
	filter := ldap.BuildRuleFilter(types.ObjectType(rule.ObjectType), conditionGroups, types.JoinOperator(rule.GroupJoinOperator))
	result.GeneratedFilter = filter

	baseDN := resolveBaseDN(rule, conn)
	if baseDN == "" {
		return nil, fmt.Errorf("base DN could not be resolved from rule or connection")
	}
	if rule.BaseDNOverride == nil || *rule.BaseDNOverride == "" {
		result.Warnings = append(result.Warnings, "Using connection default base DN")
	}

	entries, err := client.Search(baseDN, resolveScope(rule, conn), filter, collectAttributes(rule))
	if err != nil {
		return nil, fmt.Errorf("search failed: %w", err)
	}

	for _, entry := range entries {
		matched := MatchedObject{
			DN:         entry.DN,
			ObjectType: rule.ObjectType,
			Attributes: make(map[string][]string),
		}
		for _, attr := range entry.Attributes {
			matched.Attributes[attr.Name] = attr.Values
		}
		matched.CanonicalName = ldap.CanonicalName(entry.DN, entry.GetAttributeValue("canonicalName"))
		result.MatchedObjects = append(result.MatchedObjects, matched)
	}

	result.PlannedActions = e.planActions(rule, result.MatchedObjects, client)

	e.logger.Info("RuleEngine", "Preview complete: %d objects matched, %d actions planned",
		len(result.MatchedObjects), len(result.PlannedActions))

	return result, nil
}

// Execute runs the rule against the directory and performs its actions.
// The caller is responsible for providing an already-bound LDAP client and
// for persisting the returned ExecutionResult if desired.
func (e *Engine) Execute(ctx context.Context, rule *models.Rule, conn *models.ADConnection, client *ldap.Client) *ExecutionResult {
	started := time.Now().UTC()
	result := &ExecutionResult{
		RuleID:    rule.ID,
		Status:    types.RunStatusRunning,
		StartedAt: started,
	}

	e.logger.Info("RuleEngine", "Executing rule '%s' (ID: %s)", rule.Name, rule.ID)

	conditionGroups := buildConditionGroups(rule)
	filter := ldap.BuildRuleFilter(types.ObjectType(rule.ObjectType), conditionGroups, types.JoinOperator(rule.GroupJoinOperator))

	baseDN := resolveBaseDN(rule, conn)
	if baseDN == "" {
		return e.failResult(result, started, "base DN could not be resolved from rule or connection")
	}

	entries, err := client.Search(baseDN, resolveScope(rule, conn), filter, collectAttributes(rule))
	if err != nil {
		return e.failResult(result, started, fmt.Sprintf("search failed: %v", err))
	}

	result.ObjectsMatched = len(entries)

	if types.ExecutionMode(rule.ExecutionMode) == types.ExecutionModePreviewOnly {
		e.finalize(result, started, types.RunStatusCompleted)
		e.logger.Info("RuleEngine", "Preview-only run completed: %d matched", result.ObjectsMatched)
		return result
	}

	executor := newActionExecutor(client)
	cancelled := false
	matchedDNs := make([]string, 0, len(entries))

objectLoop:
	for _, entry := range entries {
		select {
		case <-ctx.Done():
			cancelled = true
			result.Errors = append(result.Errors, "execution cancelled")
			break objectLoop
		default:
		}

		matched := MatchedObject{
			DN:         entry.DN,
			ObjectType: rule.ObjectType,
			Attributes: make(map[string][]string),
		}
		for _, attr := range entry.Attributes {
			matched.Attributes[attr.Name] = attr.Values
		}
		matchedDNs = append(matchedDNs, entry.DN)

		for i := range rule.Actions {
			action := &rule.Actions[i]
			if !action.IsEnabled || isSetAction(action.ActionType) {
				continue // set-level actions run once after the loop
			}
			actionStart := time.Now()
			outcome := executor.execute(action, rule, matched)
			dur := time.Since(actionStart)

			result.ActionResults = append(result.ActionResults, ActionResult{
				ActionID:   outcome.ActionID,
				ActionType: outcome.ActionType,
				ObjectDN:   outcome.ObjectDN,
				Success:    outcome.Success,
				Error:      outcome.Error,
				Duration:   dur,
				Details:    outcome.Details,
			})

			if outcome.Success {
				result.ActionsExecuted++
			} else {
				result.ActionsFailed++
				result.Errors = append(result.Errors,
					fmt.Sprintf("action %s on %s failed: %s", outcome.ActionType, outcome.ObjectDN, outcome.Error))
				if rule.StopOnError {
					break objectLoop
				}
			}
		}
		result.ObjectsProcessed++
	}

	// Set-level actions (SyncGroupMembership) reconcile the whole matched set
	// against a target group's membership in one pass.
	if !cancelled {
		for i := range rule.Actions {
			action := &rule.Actions[i]
			if !action.IsEnabled || !isSetAction(action.ActionType) {
				continue
			}
			actionStart := time.Now()
			outcomes := e.reconcileMembership(action, rule, matchedDNs, client, e.managed)
			dur := time.Since(actionStart)
			for _, oc := range outcomes {
				oc.Duration = dur
				result.ActionResults = append(result.ActionResults, oc)
				if oc.Success {
					result.ActionsExecuted++
				} else {
					result.ActionsFailed++
					result.Errors = append(result.Errors,
						fmt.Sprintf("sync %s on %s failed: %s", oc.ActionType, oc.ObjectDN, oc.Error))
				}
			}
			if result.ActionsFailed > 0 && rule.StopOnError {
				break
			}
		}
	}

	status := types.RunStatusCompleted
	if cancelled {
		status = types.RunStatusCancelled
	} else if result.ActionsFailed > 0 && rule.StopOnError {
		status = types.RunStatusFailed
	}
	e.finalize(result, started, status)

	e.logger.Info("RuleEngine", "Execution finished: matched=%d processed=%d executed=%d failed=%d status=%s",
		result.ObjectsMatched, result.ObjectsProcessed, result.ActionsExecuted, result.ActionsFailed, status)

	return result
}

func (e *Engine) failResult(result *ExecutionResult, started time.Time, msg string) *ExecutionResult {
	result.Errors = append(result.Errors, msg)
	e.finalize(result, started, types.RunStatusFailed)
	return result
}

func (e *Engine) finalize(result *ExecutionResult, started time.Time, status types.RunStatus) {
	result.CompletedAt = time.Now().UTC()
	result.Duration = result.CompletedAt.Sub(started)
	result.Status = status
}

func buildConditionGroups(rule *models.Rule) []ldap.ConditionGroup {
	var groups []ldap.ConditionGroup
	for _, g := range rule.ConditionGroups {
		if !g.IsEnabled {
			continue
		}
		group := ldap.ConditionGroup{
			JoinOperator: types.JoinOperator(g.JoinOperator),
			Negate:       g.Negate,
		}
		for _, c := range g.Conditions {
			if !c.IsEnabled {
				continue
			}
			cond := ldap.Condition{
				Attribute:     c.AttributeName,
				Operator:      types.ConditionOperator(c.Operator),
				Negate:        c.Negate,
				CaseSensitive: c.CaseSensitive,
			}
			if c.ComparisonValue != nil {
				cond.Value = *c.ComparisonValue
			}
			if c.CustomLdapExpression != nil {
				cond.CustomLdap = *c.CustomLdapExpression
			}
			group.Conditions = append(group.Conditions, cond)
		}
		groups = append(groups, group)
	}
	return groups
}

func (e *Engine) planActions(rule *models.Rule, objects []MatchedObject, client membershipClient) []PlannedAction {
	var planned []PlannedAction
	matchedDNs := make([]string, 0, len(objects))
	for _, o := range objects {
		matchedDNs = append(matchedDNs, o.DN)
	}

	for i := range rule.Actions {
		action := &rule.Actions[i]
		if !action.IsEnabled {
			continue
		}

		if isSetAction(action.ActionType) {
			planned = append(planned, e.planSyncAction(action, rule, matchedDNs, client)...)
			continue
		}

		for _, obj := range objects {
			planned = append(planned, PlannedAction{
				ActionID:    action.ID,
				ActionType:  action.ActionType,
				TargetDN:    obj.DN,
				Description: fmt.Sprintf("%s on %s", action.ActionType, obj.DN),
				IsChange:    true,
			})
		}
	}
	return planned
}

// planSyncAction computes an accurate, non-mutating preview for a
// SyncGroupMembership action: a summary line plus one planned entry per member
// that would be added or removed.
func (e *Engine) planSyncAction(action *models.RuleAction, rule *models.Rule,
	matchedDNs []string, client membershipClient) []PlannedAction {

	plan := planMembership(action, rule, matchedDNs, client, e.managed, false)
	if plan.Err != nil {
		return []PlannedAction{{
			ActionID:    action.ID,
			ActionType:  string(types.ActionSyncGroupMembership),
			TargetDN:    plan.GroupDN,
			Description: "cannot sync: " + plan.Err.Error(),
			IsChange:    false,
		}}
	}

	var planned []PlannedAction
	summary := fmt.Sprintf("sync %s: +%d add / -%d remove (%d already in sync)",
		plan.GroupDN, len(plan.ToAdd), len(plan.ToRemove), plan.Unchanged)
	if plan.GroupCreated {
		summary = "create group + " + summary
	}
	planned = append(planned, PlannedAction{
		ActionID:    action.ID,
		ActionType:  string(types.ActionSyncGroupMembership),
		TargetDN:    plan.GroupDN,
		Description: summary,
		IsChange:    plan.GroupCreated || len(plan.ToAdd) > 0 || len(plan.ToRemove) > 0,
	})
	for _, dn := range plan.ToAdd {
		planned = append(planned, PlannedAction{
			ActionID:    action.ID,
			ActionType:  string(types.ActionAddToGroup),
			TargetDN:    dn,
			Description: "add to " + plan.GroupDN,
			IsChange:    true,
		})
	}
	for _, dn := range plan.ToRemove {
		planned = append(planned, PlannedAction{
			ActionID:    action.ID,
			ActionType:  string(types.ActionRemoveFromGroupIfNoMatch),
			TargetDN:    dn,
			Description: "remove from " + plan.GroupDN + " (no longer matches)",
			IsChange:    true,
		})
	}
	return planned
}

func resolveBaseDN(rule *models.Rule, conn *models.ADConnection) string {
	if rule.BaseDNOverride != nil && *rule.BaseDNOverride != "" {
		return *rule.BaseDNOverride
	}
	if conn != nil {
		return conn.RootDN
	}
	return ""
}

func resolveScope(rule *models.Rule, conn *models.ADConnection) int {
	scope := ""
	if rule.SearchScopeOverride != nil {
		scope = *rule.SearchScopeOverride
	}
	if scope == "" && conn != nil {
		scope = conn.DefaultSearchScope
	}
	switch scope {
	case "Base":
		return ldapv3.ScopeBaseObject
	case "OneLevel":
		return ldapv3.ScopeSingleLevel
	default:
		return ldapv3.ScopeWholeSubtree
	}
}

func collectAttributes(rule *models.Rule) []string {
	set := map[string]bool{
		"dn":                true,
		"cn":                true,
		"objectClass":       true,
		"sAMAccountName":    true,
		"distinguishedName": true,
		"userPrincipalName": true,
		"mail":              true,
		"memberOf":          true,
		"member":            true,
		"canonicalName":     true,
	}
	for _, g := range rule.ConditionGroups {
		for _, c := range g.Conditions {
			if c.AttributeName != "" {
				set[c.AttributeName] = true
			}
		}
	}
	attrs := make([]string, 0, len(set))
	for k := range set {
		attrs = append(attrs, k)
	}
	return attrs
}