<!-- [DEF:MigrationDashboard:Component] -->
<!--
@SEMANTICS: migration, dashboard, environment, selection, database-replacement
@PURPOSE:   Main dashboard for configuring and starting migrations.
@LAYER:     Page
@RELATION:  USES -> EnvSelector

@INVARIANT: Migration cannot start without source and target environments.
-->

<script lang="ts">
  // [SECTION: IMPORTS]
  import { onMount } from 'svelte';
  import EnvSelector from '../../components/EnvSelector.svelte';
  import DashboardGrid from '../../components/DashboardGrid.svelte';
  import MappingTable from '../../components/MappingTable.svelte';
  import MissingMappingModal from '../../components/MissingMappingModal.svelte';
  import type { DashboardMetadata, DashboardSelection } from '../../types/dashboard';
  // [/SECTION]

  // [SECTION: STATE]
  let environments: any[] = [];
  let sourceEnvId = "";
  let targetEnvId = "";
  let replaceDb = false;
  let loading = true;
  let error = "";
  let dashboards: DashboardMetadata[] = [];
  let selectedDashboardIds: number[] = [];
  let sourceDatabases: any[] = [];
  let targetDatabases: any[] = [];
  let mappings: any[] = [];
  let suggestions: any[] = [];
  let fetchingDbs = false;
  // [/SECTION]

  // [DEF:fetchEnvironments:Function]
  /**
   * @purpose Fetches the list of environments from the API.
   * @post    environments state is updated.
   */
  async function fetchEnvironments() {
    try {
      const response = await fetch('/api/environments');
      if (!response.ok) throw new Error('Failed to fetch environments');
      environments = await response.json();
    } catch (e) {
      error = e.message;
    } finally {
      loading = false;
    }
  }
  // [/DEF:fetchEnvironments]

  // [DEF:fetchDashboards:Function]
  /**
   * @purpose Fetches dashboards for the selected source environment.
   * @param envId The environment ID.
   * @post    dashboards state is updated.
   */
  async function fetchDashboards(envId: string) {
    try {
      const response = await fetch(`/api/environments/${envId}/dashboards`);
      if (!response.ok) throw new Error('Failed to fetch dashboards');
      dashboards = await response.json();
      selectedDashboardIds = []; // Reset selection when env changes
    } catch (e) {
      error = e.message;
      dashboards = [];
    }
  }
  // [/DEF:fetchDashboards]

  onMount(fetchEnvironments);

  // Reactive: fetch dashboards when source env changes
  $: if (sourceEnvId) fetchDashboards(sourceEnvId);

  // [DEF:fetchDatabases:Function]
  /**
   * @purpose Fetches databases from both environments and gets suggestions.
   */
  async function fetchDatabases() {
    if (!sourceEnvId || !targetEnvId) return;
    fetchingDbs = true;
    error = "";
    
    try {
      const [srcRes, tgtRes, mapRes, sugRes] = await Promise.all([
        fetch(`/api/environments/${sourceEnvId}/databases`),
        fetch(`/api/environments/${targetEnvId}/databases`),
        fetch(`/api/mappings?source_env_id=${sourceEnvId}&target_env_id=${targetEnvId}`),
        fetch(`/api/mappings/suggest`, {
          method: 'POST',
          headers: { 'Content-Type': 'application/json' },
          body: JSON.stringify({ source_env_id: sourceEnvId, target_env_id: targetEnvId })
        })
      ]);

      if (!srcRes.ok || !tgtRes.ok) throw new Error('Failed to fetch databases from environments');
      
      sourceDatabases = await srcRes.json();
      targetDatabases = await tgtRes.json();
      mappings = await mapRes.json();
      suggestions = await sugRes.json();
    } catch (e) {
      error = e.message;
    } finally {
      fetchingDbs = false;
    }
  }
  // [/DEF:fetchDatabases]

  // [DEF:handleMappingUpdate:Function]
  /**
   * @purpose Saves a mapping to the backend.
   */
  async function handleMappingUpdate(event: CustomEvent) {
    const { sourceUuid, targetUuid } = event.detail;
    const sDb = sourceDatabases.find(d => d.uuid === sourceUuid);
    const tDb = targetDatabases.find(d => d.uuid === targetUuid);
    
    if (!sDb || !tDb) return;

    try {
      const response = await fetch('/api/mappings', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          source_env_id: sourceEnvId,
          target_env_id: targetEnvId,
          source_db_uuid: sourceUuid,
          target_db_uuid: targetUuid,
          source_db_name: sDb.database_name,
          target_db_name: tDb.database_name
        })
      });

      if (!response.ok) throw new Error('Failed to save mapping');
      
      const savedMapping = await response.json();
      mappings = [...mappings.filter(m => m.source_db_uuid !== sourceUuid), savedMapping];
    } catch (e) {
      error = e.message;
    }
  }
  // [/DEF:handleMappingUpdate]

  // [DEF:startMigration:Function]
  /**
   * @purpose Starts the migration process.
   * @pre     sourceEnvId and targetEnvId must be set and different.
   */
  async function startMigration() {
    if (!sourceEnvId || !targetEnvId) {
      error = "Please select both source and target environments.";
      return;
    }
    if (sourceEnvId === targetEnvId) {
      error = "Source and target environments must be different.";
      return;
    }
    if (selectedDashboardIds.length === 0) {
      error = "Please select at least one dashboard to migrate.";
      return;
    }

    error = "";
    try {
      const selection: DashboardSelection = {
        selected_ids: selectedDashboardIds,
        source_env_id: sourceEnvId,
        target_env_id: targetEnvId
      };
      console.log(`[MigrationDashboard][Action] Starting migration with selection:`, selection);
      const response = await fetch('/api/migration/execute', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(selection)
      });
      console.log(`[MigrationDashboard][Action] API response status: ${response.status}`);
      if (!response.ok) throw new Error(`Failed to start migration: ${response.status} ${response.statusText}`);
      const result = await response.json();
      console.log(`[MigrationDashboard][Action] Migration started: ${result.task_id} - ${result.message}`);
      // TODO: Show success message or redirect to task status
    } catch (e) {
      console.error(`[MigrationDashboard][Failure] Migration failed:`, e);
      error = e.message;
    }
  }
  // [/DEF:startMigration]
</script>

<!-- [SECTION: TEMPLATE] -->
<div class="max-w-4xl mx-auto p-6">
  <h1 class="text-2xl font-bold mb-6">Migration Dashboard</h1>

  {#if loading}
    <p>Loading environments...</p>
  {:else if error}
    <div class="bg-red-100 border border-red-400 text-red-700 px-4 py-3 rounded mb-4">
      {error}
    </div>
  {/if}

  <div class="grid grid-cols-1 md:grid-cols-2 gap-6 mb-8">
    <EnvSelector
      label="Source Environment"
      bind:selectedId={sourceEnvId}
      {environments}
    />
    <EnvSelector
      label="Target Environment"
      bind:selectedId={targetEnvId}
      {environments}
    />
  </div>

  <!-- [DEF:DashboardSelectionSection] -->
  <div class="mb-8">
    <h2 class="text-lg font-medium mb-4">Select Dashboards</h2>
    
    {#if sourceEnvId}
      <DashboardGrid
        {dashboards}
        bind:selectedIds={selectedDashboardIds}
      />
    {:else}
      <p class="text-gray-500 italic">Select a source environment to view dashboards.</p>
    {/if}
  </div>
  <!-- [/DEF:DashboardSelectionSection] -->


  <div class="flex items-center mb-4">
    <input
      id="replace-db"
      type="checkbox"
      bind:checked={replaceDb}
      on:change={() => { if (replaceDb && sourceDatabases.length === 0) fetchDatabases(); }}
      class="h-4 w-4 text-indigo-600 focus:ring-indigo-500 border-gray-300 rounded"
    />
    <label for="replace-db" class="ml-2 block text-sm text-gray-900">
      Replace Database (Apply Mappings)
    </label>
  </div>

  {#if replaceDb}
    <div class="mb-8 p-4 border rounded-md bg-gray-50">
      <h3 class="text-md font-medium mb-4">Database Mappings</h3>
      {#if fetchingDbs}
        <p>Loading databases and suggestions...</p>
      {:else if sourceDatabases.length > 0}
        <MappingTable
          {sourceDatabases}
          {targetDatabases}
          {mappings}
          {suggestions}
          on:update={handleMappingUpdate}
        />
      {:else if sourceEnvId && targetEnvId}
        <button
          on:click={fetchDatabases}
          class="text-indigo-600 hover:text-indigo-500 text-sm font-medium"
        >
          Refresh Databases & Suggestions
        </button>
      {/if}
    </div>
  {/if}

  <button
    on:click={startMigration}
    disabled={!sourceEnvId || !targetEnvId || sourceEnvId === targetEnvId || selectedDashboardIds.length === 0}
    class="inline-flex items-center px-4 py-2 border border-transparent text-sm font-medium rounded-md shadow-sm text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500 disabled:bg-gray-400"
  >
    Start Migration
  </button>
</div>
<!-- [/SECTION] -->

<style>
  /* Page specific styles */
</style>

<!-- [/DEF:MigrationDashboard] -->
