package wages

import (
	"context"
	"errors"
	"time"

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

// ErrNoDatabase is returned when no pool is configured.
var ErrNoDatabase = errors.New("wages: no database configured")

// Service reads the cached BLS wage baseline.
type Service struct{ db *tenant.DB }

// NewService builds the service. db may be nil (then calls return ErrNoDatabase).
func NewService(db *tenant.DB) *Service { return &Service{db: db} }

// Baseline returns the wage baseline grouped by occupation, each with its Hawaii and New Mexico
// annual mean and median wages.
func (s *Service) Baseline(ctx context.Context) ([]WageBaseline, error) {
	if s.db == nil || s.db.Pool == nil {
		return nil, ErrNoDatabase
	}
	rows, err := dbgen.New(s.db.Pool).ListBlsWages(ctx)
	if err != nil {
		return nil, err
	}

	order := []string{}                    // preserve first seen occupation order
	byOcc := map[string]*WageBaseline{}    // occupation_code to baseline
	areaIdx := map[string]map[string]int{} // occupation_code to area to index in Areas
	syncedAt := time.Time{}

	for _, r := range rows {
		wb, ok := byOcc[r.OccupationCode]
		if !ok {
			wb = &WageBaseline{
				OccupationCode:  r.OccupationCode,
				OccupationTitle: r.OccupationTitle,
				Role:            r.Role,
				Year:            r.PeriodYear,
				Source:          "BLS OEWS",
			}
			byOcc[r.OccupationCode] = wb
			areaIdx[r.OccupationCode] = map[string]int{}
			order = append(order, r.OccupationCode)
		}
		ai, ok := areaIdx[r.OccupationCode][r.Area]
		if !ok {
			wb.Areas = append(wb.Areas, AreaWage{Area: r.Area, AreaName: r.AreaName})
			ai = len(wb.Areas) - 1
			areaIdx[r.OccupationCode][r.Area] = ai
		}
		val := ""
		if r.Value != nil {
			val = r.Value.StringFixed(0)
		}
		switch r.Metric {
		case "annual_mean":
			wb.Areas[ai].AnnualMean = val
		case "annual_median":
			wb.Areas[ai].AnnualMedian = val
		}
		if r.SyncedAt.After(syncedAt) {
			syncedAt = r.SyncedAt
		}
	}

	out := make([]WageBaseline, 0, len(order))
	for _, code := range order {
		wb := byOcc[code]
		if !syncedAt.IsZero() {
			wb.SyncedAt = syncedAt.Format(time.RFC3339)
		}
		out = append(out, *wb)
	}
	return out, nil
}