import type { SupabaseClient } from '@supabase/supabase-js'
import type { AuditLogEntry, AuditAction } from '@/types'

/**
 * Audit Service - Read-only service for the audit log
 *
 * The audit log is written exclusively by database triggers (SECURITY DEFINER).
 * This service provides read access for compliance reporting and investigation.
 */

export interface AuditLogFilters {
  action?: AuditAction
  table_name?: string
  record_id?: string
  from_date?: string
  to_date?: string
  page?: number
  pageSize?: number
}

/**
 * Get paginated audit log entries for a user
 */
export async function getAuditLog(
  supabase: SupabaseClient,
  userId: string,
  filters: AuditLogFilters = {}
): Promise<{ data: AuditLogEntry[]; count: number }> {
  const page = filters.page ?? 1
  const pageSize = filters.pageSize ?? 50
  const offset = (page - 1) * pageSize

  let query = supabase
    .from('audit_log')
    .select('*', { count: 'exact' })
    .eq('user_id', userId)
    .order('created_at', { ascending: false })
    .range(offset, offset + pageSize - 1)

  if (filters.action) {
    query = query.eq('action', filters.action)
  }
  if (filters.table_name) {
    query = query.eq('table_name', filters.table_name)
  }
  if (filters.record_id) {
    query = query.eq('record_id', filters.record_id)
  }
  if (filters.from_date) {
    query = query.gte('created_at', filters.from_date)
  }
  if (filters.to_date) {
    query = query.lte('created_at', filters.to_date)
  }

  const { data, error, count } = await query

  if (error) {
    throw new Error(`Failed to fetch audit log: ${error.message}`)
  }

  return {
    data: (data as AuditLogEntry[]) || [],
    count: count ?? 0,
  }
}

/**
 * Get full history of a single record (all mutations)
 */
export async function getEntityHistory(
  supabase: SupabaseClient,
  userId: string,
  tableName: string,
  recordId: string
): Promise<AuditLogEntry[]> {

  const { data, error } = await supabase
    .from('audit_log')
    .select('*')
    .eq('user_id', userId)
    .eq('table_name', tableName)
    .eq('record_id', recordId)
    .order('created_at', { ascending: true })

  if (error) {
    throw new Error(`Failed to fetch entity history: ${error.message}`)
  }

  return (data as AuditLogEntry[]) || []
}

/**
 * Trace the correction chain for a journal entry:
 * original → storno (reversal) → corrected entry
 */
export async function getCorrectionChain(
  supabase: SupabaseClient,
  userId: string,
  journalEntryId: string
): Promise<AuditLogEntry[]> {

  // First, find the entry and its linked entries
  const { data: entry, error: entryError } = await supabase
    .from('journal_entries')
    .select('id, reverses_id, reversed_by_id, correction_of_id')
    .eq('id', journalEntryId)
    .eq('user_id', userId)
    .single()

  if (entryError || !entry) {
    throw new Error('Journal entry not found')
  }

  // Collect all related entry IDs
  const relatedIds = new Set<string>([entry.id])
  if (entry.reverses_id) relatedIds.add(entry.reverses_id)
  if (entry.reversed_by_id) relatedIds.add(entry.reversed_by_id)
  if (entry.correction_of_id) relatedIds.add(entry.correction_of_id)

  // Also look for entries that reference this one
  const { data: referencing } = await supabase
    .from('journal_entries')
    .select('id')
    .eq('user_id', userId)
    .or(`reverses_id.eq.${journalEntryId},reversed_by_id.eq.${journalEntryId},correction_of_id.eq.${journalEntryId}`)

  for (const ref of referencing || []) {
    relatedIds.add(ref.id)
  }

  // Fetch audit log entries for all related IDs
  const { data, error } = await supabase
    .from('audit_log')
    .select('*')
    .eq('user_id', userId)
    .eq('table_name', 'journal_entries')
    .in('record_id', Array.from(relatedIds))
    .order('created_at', { ascending: true })

  if (error) {
    throw new Error(`Failed to fetch correction chain: ${error.message}`)
  }

  return (data as AuditLogEntry[]) || []
}