-- 002_backfill_inbox_ats.sql
-- Manual one-shot: backfill the inbox-side ATS columns that gained a writer in
-- job/candidate/views.py::CandidateScoring._sync_inbox_ats. Before that change,
-- inbox_messages.ats_score / ats_band were never written and ats_results held
-- 0 rows, so messages scored earlier show null on the Applications tab.
--
-- Idempotent: the UPDATE only touches rows still missing a score, and the
-- INSERT skips any application that already has an ats_results row.
-- Applied automatically at startup by alembic_setup.run_manual_sql() once the
-- schema is at head; recorded in manual_migrations. Safe to re-run by hand.
--
-- The Candidates.inbox_message_id join is historical: that column is dropped
-- after revision b7d4e8f1a203. Those three statements run only when the column
-- is still present (a DB that has not yet reached that revision). Fresh installs
-- skip them — there is no pre-denorm history to copy.

DO $backfill$
BEGIN
  IF EXISTS (
    SELECT 1 FROM information_schema.columns
    WHERE table_schema = 'app'
      AND table_name = 'candidates'
      AND column_name = 'inbox_message_id'
  ) THEN
    -- Winning score per message, mirroring CandidateView._recommendation precedence:
    -- the completed score against the ASSIGNED job wins, else the newest completed.
    EXECUTE $sql$
      WITH ranked AS (
          SELECT
              c.inbox_message_id,
              c.job_id,
              c.match_score,
              c.model,
              c.updated_at,
              ROW_NUMBER() OVER (
                  PARTITION BY c.inbox_message_id
                  ORDER BY (c.job_id = m.assigned_job_post_id) DESC NULLS LAST,
                           c.updated_at DESC
              ) AS rn
          FROM app.candidates c
          JOIN app.inbox_messages m ON m.id = c.inbox_message_id
          WHERE c.status = 'completed'
            AND c.inbox_message_id IS NOT NULL
      )
      UPDATE app.inbox_messages m
      SET ats_score = r.match_score,
          ats_band = CASE
              WHEN r.match_score >= 82 THEN 'Strong Match'
              WHEN r.match_score >= 65 THEN 'Potential Match'
              ELSE 'Weak Match'
          END
      FROM ranked r
      WHERE r.rn = 1
        AND m.id = r.inbox_message_id
        AND m.ats_score IS NULL
    $sql$;

    -- One current ats_results row per already-scored application. computed_at takes
    -- the candidates row's timestamp so the history reflects when the score happened.
    -- inbox can hold several join rows per message; DISTINCT ON keeps the newest.
    EXECUTE $sql$
      WITH ranked AS (
          SELECT
              c.inbox_message_id,
              c.job_id,
              c.match_score,
              c.model,
              c.updated_at,
              ROW_NUMBER() OVER (
                  PARTITION BY c.inbox_message_id
                  ORDER BY (c.job_id = m.assigned_job_post_id) DESC NULLS LAST,
                           c.updated_at DESC
              ) AS rn
          FROM app.candidates c
          JOIN app.inbox_messages m ON m.id = c.inbox_message_id
          WHERE c.status = 'completed'
            AND c.inbox_message_id IS NOT NULL
      ),
      links AS (
          SELECT DISTINCT ON (message_id) message_id, id AS inbox_id
          FROM app.inbox
          ORDER BY message_id, created_at DESC
      )
      INSERT INTO app.ats_results
          (id, inbox_id, job_post_id, overall_score, band, is_current,
           superseded_by_id, model_name, computed_at, created_at)
      SELECT
          gen_random_uuid(),
          l.inbox_id,
          r.job_id,
          r.match_score,
          CASE
              WHEN r.match_score >= 82 THEN 'Strong Match'
              WHEN r.match_score >= 65 THEN 'Potential Match'
              ELSE 'Weak Match'
          END,
          true,
          NULL,
          r.model,
          r.updated_at,
          NOW()
      FROM ranked r
      JOIN links l ON l.message_id = r.inbox_message_id
      WHERE r.rn = 1
        AND NOT EXISTS (
          SELECT 1 FROM app.ats_results a WHERE a.inbox_id = l.inbox_id
        )
    $sql$;

    -- Older inbox history rows predate candidate_id; link the current ones back to
    -- the candidates row that produced them.
    EXECUTE $sql$
      UPDATE app.ats_results a
      SET candidate_id = c.id
      FROM app.inbox i
      JOIN app.candidates c ON c.inbox_message_id = i.message_id AND c.status = 'completed'
      WHERE a.inbox_id = i.id
        AND a.candidate_id IS NULL
        AND c.job_id = a.job_post_id
    $sql$;
  END IF;
END
$backfill$;

-- inbox.ats_id -> the CURRENT ats_results row for that application, so the
-- score is one direct id join away. Newest current row wins if several exist.
UPDATE app.inbox i
SET ats_id = a.id,
    updated_at = NOW()
FROM (
    SELECT DISTINCT ON (inbox_id) inbox_id, id
    FROM app.ats_results
    WHERE is_current AND inbox_id IS NOT NULL
    ORDER BY inbox_id, computed_at DESC
) a
WHERE a.inbox_id = i.id
  AND i.ats_id IS DISTINCT FROM a.id;

-- Upload-sourced scores get history rows too: inbox_id stays NULL (no inbox
-- application exists) and the row links via candidate_id instead.
INSERT INTO app.ats_results
    (id, inbox_id, candidate_id, job_post_id, overall_score, band, is_current,
     superseded_by_id, model_name, computed_at, created_at)
SELECT
    gen_random_uuid(),
    NULL,
    c.id,
    c.job_id,
    c.match_score,
    CASE
        WHEN c.match_score >= 82 THEN 'Strong Match'
        WHEN c.match_score >= 65 THEN 'Potential Match'
        ELSE 'Weak Match'
    END,
    true,
    NULL,
    c.model,
    c.updated_at,
    NOW()
FROM app.candidates c
WHERE c.status = 'completed'
  AND c.source = 'upload'
  AND NOT EXISTS (
      SELECT 1 FROM app.ats_results a WHERE a.candidate_id = c.id
  );