package matching

import (
	"context"
	"encoding/json"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"

	"github.com/missionworkforce/missionmatch/internal/platform/audit"
	"github.com/missionworkforce/missionmatch/internal/platform/database/dbgen"
)

// SupportView is one candidate who can support a mission today, read from the persisted screenMATCH
// qualification (the stored artifact), never a rescore. It carries the frozen total and band so the
// number matches what screenMATCH and slateMATCH show for the same candidate.
type SupportView struct {
	CandidateID string `json:"candidate_id"`
	FullName    string `json:"full_name"`
	Total       string `json:"total_score"`
	Band        string `json:"band"`
	BandLabel   string `json:"band_label"`
	Available   bool   `json:"available"`
	EvaluatedAt string `json:"evaluated_at"`
}

// WhoCanSupport returns the candidates with a persisted screenMATCH qualification for one requirement,
// best first (the missionMATCH "who can support this mission today" rollup). It READS the stored
// candidate_evaluations rows; it never rescores the pool, so the rollup agrees with the screen and the
// slate to the cent. An empty result means no one has been screened against the requirement yet.
func (s *Service) WhoCanSupport(ctx context.Context, requirementID uuid.UUID) ([]SupportView, error) {
	if s.db == nil {
		return nil, ErrNoDatabase
	}
	var out []SupportView
	err := s.db.RunInTenantTx(ctx, func(ctx context.Context, tx pgx.Tx) error {
		rows, e := dbgen.New(tx).ListEvaluationsForRequirement(ctx, requirementID)
		if e != nil {
			return e
		}
		out = make([]SupportView, len(rows))
		for i, r := range rows {
			out[i] = SupportView{
				CandidateID: r.CandidateID.String(),
				FullName:    r.FullName,
				Total:       r.TotalScore.StringFixed(2),
				Band:        r.Band,
				BandLabel:   bandLabel(r.Band),
				Available:   r.Available,
				EvaluatedAt: r.EvaluatedAt.Format("2006-01-02"),
			}
		}
		// Cross tool data access: missionMATCH is reading screenMATCH's persisted evaluations. Record it
		// for traceability when there is data to read (the requirement and a count only, never candidate
		// PII or a score). Fail closed if the trace cannot be written.
		if len(out) > 0 {
			payload, _ := json.Marshal(map[string]any{
				"reader": "missionMATCH", "source": "screenMATCH.evaluations",
				"requirement_id": requirementID.String(), "count": len(out),
			})
			if e := s.auditOnTx(ctx, tx, audit.Event{
				Action: "aedt.cross_tool.read", EntityType: "requirement", EntityID: requirementID.String(), NewValues: payload,
			}); e != nil {
				return e
			}
		}
		return nil
	})
	return out, err
}