// Package lldapexport implements the LLDAP → canonical export tool (spec §7 — migration contract).
// It reads all users and groups from the LLDAP directory via a UserRepository, validates each
// entry against the canonical LDAP schema, and writes a canonical-export.yaml snapshot.
package lldapexport

import (
	"context"
	"fmt"
	"os"
	"time"

	"gopkg.in/yaml.v3"

	"keycape/internal/domain"
	"keycape/internal/server/telemetry"
	"keycape/internal/validator"
)

// ExportResult is the structured output of a single export run.
type ExportResult struct {
	Users                 []domain.User       `yaml:"users"`
	Groups                []domain.Group      `yaml:"groups"`
	Memberships           []domain.Membership `yaml:"memberships"`
	ExportedAt            time.Time           `yaml:"exportedAt"`
	ProfileVersion        string              `yaml:"profileVersion"`
	IncompatibilityReport []string            `yaml:"incompatibilityReport,omitempty"`
}

// Exporter reads from a UserRepository, validates, and writes canonical-export.yaml.
type Exporter struct {
	repo    domain.UserRepository
	mode    validator.Mode
	emitter telemetry.Emitter
}

// New creates a new Exporter.
func New(repo domain.UserRepository, mode validator.Mode, emitter telemetry.Emitter) *Exporter {
	return &Exporter{
		repo:    repo,
		mode:    mode,
		emitter: emitter,
	}
}

// Export reads all users and groups, validates them, builds ExportResult,
// emits telemetry, and writes the YAML file to outputFile.
// Validation failures are captured in IncompatibilityReport — they are not fatal.
func (e *Exporter) Export(ctx context.Context, outputFile string) (*ExportResult, error) {
	// 1. List all users from the repository.
	users, err := e.repo.ListUsers(ctx)
	if err != nil {
		return nil, fmt.Errorf("lldapexport: list users: %w", err)
	}

	// 2. List all groups by looking up groups for each user's DN.
	//    Since UserRepository.LookupGroups takes a userDN, we collect groups
	//    from all users and deduplicate by group ID.
	groupMap := make(map[string]domain.Group)
	for _, u := range users {
		userGroups, err := e.repo.LookupGroups(ctx, u.ID)
		if err != nil {
			// Non-fatal: log in incompatibility report.
			continue
		}
		for _, g := range userGroups {
			if _, seen := groupMap[g.ID]; !seen {
				groupMap[g.ID] = g
			}
		}
	}
	groups := make([]domain.Group, 0, len(groupMap))
	for _, g := range groupMap {
		groups = append(groups, g)
	}

	// 3. Validate each user against the canonical LDAP schema.
	var incompatibilities []string
	validatedUsers := make([]domain.User, 0, len(users))
	for _, u := range users {
		snap := validator.Snapshot{Users: []domain.User{u}}
		report := validator.Validate(snap, e.mode)
		if !report.Passed {
			for _, r := range report.Structural {
				if !r.Passed {
					incompatibilities = append(incompatibilities,
						fmt.Sprintf("user %q structural/%s: %s", u.Username, r.Rule, r.Message))
				}
			}
			for _, r := range report.Semantic {
				if !r.Passed {
					incompatibilities = append(incompatibilities,
						fmt.Sprintf("user %q semantic/%s: %s", u.Username, r.Rule, r.Message))
				}
			}
		}
		validatedUsers = append(validatedUsers, u)
	}

	// 4. Build memberships from group member lists.
	var memberships []domain.Membership
	for _, g := range groups {
		for _, memberID := range g.Members {
			memberships = append(memberships, domain.Membership{
				UserID:  memberID,
				GroupID: g.ID,
			})
		}
	}

	// 5. Build ExportResult.
	result := &ExportResult{
		Users:                 validatedUsers,
		Groups:                groups,
		Memberships:           memberships,
		ExportedAt:            time.Now().UTC(),
		ProfileVersion:        "0.1",
		IncompatibilityReport: incompatibilities,
	}

	// 6. Emit migration_event telemetry.
	e.emitter.Emit(ctx, telemetry.Event{
		Timestamp: time.Now().UTC(),
		EventType: telemetry.EventMigration,
		Endpoint:  "lldap-export",
		Result:    "success",
	})

	// 7. Write YAML to output file.
	data, err := yaml.Marshal(result)
	if err != nil {
		return nil, fmt.Errorf("lldapexport: marshal YAML: %w", err)
	}
	if err := os.WriteFile(outputFile, data, 0o644); err != nil {
		return nil, fmt.Errorf("lldapexport: write file %q: %w", outputFile, err)
	}

	return result, nil
}