package api

import (
	"context"
	"encoding/json"
	"fmt"
	"fuj-management/go/internal/config"
	"fuj-management/go/internal/services/membership"
	"log/slog"
	"net/http"
	"time"

	domreconcile "fuj-management/go/internal/domain/reconcile"
)

// Handler holds the shared dependencies for all /api/* routes.
type Handler struct {
	BuildVersion string
	BuildCommit  string
	BuildDate    string
	Sources      membership.Sources
	Config       config.Config
	Logger       *slog.Logger
}

// ServeVersion handles GET /api/version.
func (h *Handler) ServeVersion(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, VersionResponse{
		Tag:       h.BuildVersion,
		Commit:    h.BuildCommit,
		BuildDate: h.BuildDate,
	})
}

// ServeAdults handles GET /api/adults.
func (h *Handler) ServeAdults(w http.ResponseWriter, r *http.Request) {
	resp, err := h.AssembleAdults(r.Context())
	if err != nil {
		h.writeError(w, r, err)
		return
	}
	writeJSON(w, resp)
}

// AssembleAdults loads all data and builds the adults view model.
// Shared between the JSON API route and the HTML handler.
func (h *Handler) AssembleAdults(ctx context.Context) (AdultsResponse, error) {
	members, sortedMonths, txns, exceptions, err := h.loadAll(ctx, true)
	if err != nil {
		return AdultsResponse{}, err
	}
	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
	return buildAdultsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")), nil
}

// ServeJuniors handles GET /api/juniors.
func (h *Handler) ServeJuniors(w http.ResponseWriter, r *http.Request) {
	resp, err := h.AssembleJuniors(r.Context())
	if err != nil {
		h.writeError(w, r, err)
		return
	}
	writeJSON(w, resp)
}

// AssembleJuniors loads all data and builds the juniors view model.
// Shared between the JSON API route and the HTML handler.
func (h *Handler) AssembleJuniors(ctx context.Context) (JuniorsResponse, error) {
	members, sortedMonths, txns, exceptions, err := h.loadAll(ctx, false)
	if err != nil {
		return JuniorsResponse{}, err
	}
	result := domreconcile.Reconcile(members, sortedMonths, txns, exceptions, time.Now().Year())
	return buildJuniorsResponse(members, sortedMonths, result, txns, h.Config, time.Now().Format("2006-01")), nil
}

// ServePayments handles GET /api/payments.
func (h *Handler) ServePayments(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	txns, err := h.Sources.LoadTransactions(ctx)
	if err != nil {
		h.writeError(w, r, fmt.Errorf("load transactions: %w", err))
		return
	}
	writeJSON(w, buildPaymentsResponse(txns, h.allMemberNames(ctx)))
}

func (h *Handler) loadAll(ctx context.Context, adults bool) (
	members []domreconcile.Member,
	sortedMonths []string,
	txns []domreconcile.Transaction,
	exceptions map[domreconcile.ExceptionKey]domreconcile.Exception,
	err error,
) {
	if adults {
		members, sortedMonths, err = h.Sources.LoadAdults(ctx)
	} else {
		members, sortedMonths, err = h.Sources.LoadJuniors(ctx)
	}
	if err != nil {
		err = fmt.Errorf("load members: %w", err)
		return
	}
	txns, err = h.Sources.LoadTransactions(ctx)
	if err != nil {
		err = fmt.Errorf("load transactions: %w", err)
		return
	}
	exceptions, err = h.Sources.LoadExceptions(ctx)
	if err != nil {
		err = fmt.Errorf("load exceptions: %w", err)
	}
	return
}

func (h *Handler) allMemberNames(ctx context.Context) []string {
	var names []string
	if adults, _, err := h.Sources.LoadAdults(ctx); err == nil {
		for _, m := range adults {
			names = append(names, m.Name)
		}
	}
	if juniors, _, err := h.Sources.LoadJuniors(ctx); err == nil {
		for _, m := range juniors {
			names = append(names, m.Name)
		}
	}
	return names
}

func (h *Handler) writeError(w http.ResponseWriter, r *http.Request, err error) {
	if h.Logger != nil {
		h.Logger.Error("api error", "path", r.URL.Path, "err", err)
	}
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(http.StatusInternalServerError)
	_ = json.NewEncoder(w).Encode(map[string]string{"error": err.Error()})
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	_ = json.NewEncoder(w).Encode(v)
}