package db

import (
	"context"
	"encoding/json"
	"fmt"

	"github.com/dtoro/oikos/internal/core/app"
	"github.com/dtoro/oikos/internal/ontology"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
)

// EnsureEntityChecks derives an entity's default check_defs from the
// monitoring spec of its type (resolving per-entity `monitoring` overrides).
//
// This is the single shared hook that keeps the check graph in sync with
// entity mutations. Both the HTTP create/patch handlers and the MCP
// entity-mutation tools (create_entity, update_entity_attributes) call it so
// that flipping an entity's `monitoring` attribute regenerates checks
// regardless of which surface made the change — previously only the HTTP
// path ran check derivation, so entities mutated via MCP silently produced no
// checks (see plans/2026-08-03-session-review-haos-monitoring-capability-gaps.md, A2).
func EnsureEntityChecks(ctx context.Context, tx pgx.Tx, id uuid.UUID, slug, entityType, name string, attrs []byte) (app.DeriveResult, error) {
	tree, err := LoadTypeTree(ctx, tx)
	if err != nil {
		return app.DeriveResult{}, err
	}
	res, err := EnsureChecks(ctx, tx, tree, app.CheckTarget{
		ID: id.String(), Slug: slug, Type: entityType, Name: name, Attrs: attrs,
	})
	if err != nil {
		return res, err
	}
	app.LogDeriveResult(slug, entityType, res)
	return res, nil
}

// EnsureChecks writes the derived check_defs for one entity, idempotently.
// Derivation is pure core logic (app.Derive); this function owns the
// entity_status row, the graph host fallback, and the upserts.
func EnsureChecks(ctx context.Context, tx pgx.Tx, tree *ontology.TypeTree, t app.CheckTarget) (app.DeriveResult, error) {
	var res app.DeriveResult

	if _, err := tx.Exec(ctx,
		`INSERT INTO entity_status (entity_id, health, updated_at)
		 VALUES ($1, 'unknown', now())
		 ON CONFLICT (entity_id) DO NOTHING`, t.ID); err != nil {
		return res, fmt.Errorf("entity_status %s: %w", t.Slug, err)
	}

	defs, dres := app.Derive(tree, t, func() map[string]any {
		attrs, err := hostViaGraph(ctx, tx, t.ID)
		if err != nil {
			return nil
		}
		return attrs
	})
	res.Skipped, res.Undeclared = dres.Skipped, dres.Undeclared

	for i, def := range defs {
		created, err := writeCheck(ctx, tx, t, i, def)
		if err != nil {
			return res, fmt.Errorf("check %s/%s: %w", t.Slug, def.Kind, err)
		}
		if created {
			res.Created++
		}
	}
	return res, nil
}

// writeCheck upserts one check_def and its backing check entity.
//
// The entity upsert MUST return the row's id. The previous version generated
// a fresh uuid, inserted ON CONFLICT (slug) DO NOTHING, then wrote a
// check_defs row referencing that uuid. On any re-seed the slug already
// existed, the entity insert became a no-op, and the check_defs insert
// violated its foreign key — which aborted the whole ingest transaction and
// made every subsequent statement fail with 25P02. Because the errors were
// discarded, the only visible symptom was an unrelated failure much later.
func writeCheck(ctx context.Context, tx pgx.Tx, t app.CheckTarget, idx int, def app.CheckDef) (bool, error) {
	// The full target slug, not a truncation of it. shortSlug() took the last
	// 8 characters, so all 21 ingress routes collapsed to ".network" and
	// generated one identical check slug — they overwrote each other and 20
	// of them ended up with no check at all. It also collided service:jellyfin
	// with lxc:jellyfin. Entity slugs are unique; use them.
	checkSlug := fmt.Sprintf("check:%s:%s:%d", def.Kind, t.Slug, idx)

	newID, err := uuid.NewV7()
	if err != nil {
		newID = uuid.New()
	}

	var checkID uuid.UUID
	err = tx.QueryRow(ctx,
		`INSERT INTO entities (id, slug, type, name, state, attributes, version, created_at, updated_at)
		 VALUES ($1, $2, 'check', $2, 'active', '{}', 1, now(), now())
		 ON CONFLICT (slug) DO UPDATE SET updated_at = now()
		 RETURNING id`,
		newID, checkSlug).Scan(&checkID)
	if err != nil {
		return false, fmt.Errorf("upsert check entity %s: %w", checkSlug, err)
	}

	configJSON, err := json.Marshal(def.Config)
	if err != nil {
		return false, err
	}

	// Config is derived from the seed, so the seed wins on re-ingest and
	// attribute changes propagate. `enabled` is deliberately left alone: it
	// is operational state an operator may have toggled.
	// last_run_at is seeded to a random point inside the interval so checks
	// created together do not stay in lockstep. Every check the seed creates
	// would otherwise come due in the same instant forever: ~165 probes
	// landing at once each minute rather than spread across it. Deliberately
	// absent from the DO UPDATE below — a re-seed must not reset the schedule
	// and re-herd everything.
	tag, err := tx.Exec(ctx,
		`INSERT INTO check_defs (entity_id, target_id, target_type, kind, config, interval_s, timeout_s, enabled, last_run_at)
		 VALUES ($1, $2, $6, $3, $4, $5, 30, true,
		         now() - make_interval(secs => random() * $5::int))
		 ON CONFLICT (entity_id) DO UPDATE
		   SET target_id = EXCLUDED.target_id, target_type = EXCLUDED.target_type,
		       kind = EXCLUDED.kind,
		       config = EXCLUDED.config, interval_s = EXCLUDED.interval_s,
		       updated_at = now()`,
		checkID, t.ID, def.Kind, configJSON, def.IntervalS, t.Type)
	if err != nil {
		return false, fmt.Errorf("upsert check_def %s: %w", checkSlug, err)
	}
	return tag.RowsAffected() > 0, nil
}

// hostViaGraph returns the attributes of the entity that hosts or provides
// this one, so a service can inherit its container's address.
func hostViaGraph(ctx context.Context, tx pgx.Tx, entityID string) (map[string]any, error) {
	rows, err := tx.Query(ctx, `
		SELECT e.attributes
		FROM relationships r
		JOIN entities e ON e.id = r.source_id
		WHERE r.target_id = $1
		  AND r.valid_to IS NULL
		  -- backs-up-to points from the thing being backed up TO the target,
		  -- so walking it backwards finds the machine that writes the backups
		  -- — which is the only place a freshness check can run.
		  AND r.type IN ('provides', 'hosts', 'runs-on', 'backs-up-to')
		ORDER BY CASE r.type
		    WHEN 'provides' THEN 0 WHEN 'runs-on' THEN 1
		    WHEN 'backs-up-to' THEN 2 ELSE 3 END`,
		entityID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	for rows.Next() {
		var raw []byte
		if err := rows.Scan(&raw); err != nil {
			return nil, err
		}
		var attrs map[string]any
		if json.Unmarshal(raw, &attrs) != nil {
			continue
		}
		if resolveGraphHost(attrs) != "" {
			return attrs, nil
		}
	}
	return nil, rows.Err()
}

// resolveGraphHost mirrors app's address resolution for graph-walk results.
// It re-implements the small pure helper rather than exporting internals of
// the core package: the shapes it accepts are exactly the seed attribute
// shapes hostViaGraph can return.
func resolveGraphHost(attrs map[string]any) string {
	if attrs == nil {
		return ""
	}
	if ip, ok := attrs["lan_ip"].(string); ok && ip != "" {
		return ip
	}
	if ip, ok := attrs["public_ipv4"].(string); ok && ip != "" {
		return ip
	}
	if mesh, ok := attrs["mesh"].(map[string]any); ok {
		if nb, ok := mesh["netbird"].(map[string]any); ok {
			if ip, ok := nb["ip"].(string); ok && ip != "" {
				return ip
			}
			if fqdn, ok := nb["fqdn"].(string); ok && fqdn != "" {
				return fqdn
			}
		}
	}
	if ip, ok := attrs["mesh_ip"].(string); ok && ip != "" {
		return ip
	}
	for _, key := range []string{"host", "address", "public_host"} {
		if v, ok := attrs[key].(string); ok && v != "" {
			return v
		}
	}
	return ""
}