// Command accounted-multicase-intgr sends vouchers from a Multicase buntfil export
// to Accounted through its v1 REST API.
package main

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"os"
	"os/signal"
	"sort"
	"strings"
	"text/tabwriter"

	"simenandre.no/accounted-multicase-intgr/internal/accounted"
	"simenandre.no/accounted-multicase-intgr/internal/mapping"
	"simenandre.no/accounted-multicase-intgr/internal/multicase"
	"simenandre.no/accounted-multicase-intgr/internal/state"
	"simenandre.no/accounted-multicase-intgr/internal/xls"
)

const usage = `Usage:
  accounted-multicase-intgr check [-config config.json] [-v] EXPORT.xls
  accounted-multicase-intgr push  [-config config.json] [-dry-run] [-commit] [-state FILE] EXPORT.xls

check  parses the export and maps every voucher, without network access.
push   creates the vouchers as drafts in Accounted; -commit also posts them
       and assigns voucher numbers; -dry-run only lets the server validate.

push reads ACCOUNTED_API_KEY (gnubok_sk_..., scope bookkeeping:write),
ACCOUNTED_COMPANY_ID and optionally ACCOUNTED_URL (default https://app.accounted.se).
`

func main() {
	if len(os.Args) < 2 {
		fmt.Fprint(os.Stderr, usage)
		os.Exit(2)
	}
	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt)
	defer stop()

	var err error
	switch os.Args[1] {
	case "check":
		err = runCheck(os.Args[2:])
	case "push":
		err = runPush(ctx, os.Args[2:])
	case "-h", "--help", "help":
		fmt.Print(usage)
		return
	default:
		fmt.Fprint(os.Stderr, usage)
		os.Exit(2)
	}
	if err != nil {
		fmt.Fprintln(os.Stderr, "error:", err)
		os.Exit(1)
	}
}

type mapped struct {
	voucher multicase.Voucher
	entry   accounted.JournalEntry
	err     error
}

func load(configPath, exportPath string) (*mapping.Config, []mapped, error) {
	cfg, err := mapping.LoadConfig(configPath)
	if err != nil {
		return nil, nil, err
	}
	grid, err := xls.ReadFile(exportPath)
	if err != nil {
		return nil, nil, err
	}
	vouchers, err := multicase.Parse(grid)
	if err != nil {
		return nil, nil, err
	}
	out := make([]mapped, 0, len(vouchers))
	for _, v := range vouchers {
		e, err := cfg.Build(v)
		out = append(out, mapped{v, e, err})
	}
	return cfg, out, nil
}

func parseFlags(name string, args []string, define func(*flag.FlagSet)) (*flag.FlagSet, string, error) {
	fs := flag.NewFlagSet(name, flag.ContinueOnError)
	fs.Usage = func() { fmt.Fprint(os.Stderr, usage) }
	define(fs)
	if err := fs.Parse(args); err != nil {
		return nil, "", err
	}
	if fs.NArg() != 1 {
		return nil, "", errors.New("expected exactly one export file")
	}
	return fs, fs.Arg(0), nil
}

func runCheck(args []string) error {
	var configPath string
	var verbose bool
	_, export, err := parseFlags("check", args, func(fs *flag.FlagSet) {
		fs.StringVar(&configPath, "config", "config.json", "mapping config")
		fs.BoolVar(&verbose, "v", false, "print every mapped entry")
	})
	if err != nil {
		return err
	}
	_, items, err := load(configPath, export)
	if err != nil {
		return err
	}

	unmappedAccounts := map[string]int{}
	unmappedVAT := map[string]int{}
	var ok, empty, failed int
	var debit accounted.Money
	for _, m := range items {
		var u *mapping.UnmappedError
		switch {
		case errors.Is(m.err, mapping.ErrEmpty):
			empty++
		case errors.As(m.err, &u):
			failed++
			for _, a := range u.Accounts {
				unmappedAccounts[a]++
			}
			for _, c := range u.VATCodes {
				unmappedVAT[c]++
			}
		case m.err != nil:
			failed++
			fmt.Printf("%s: %v\n", m.voucher.Label(), m.err)
		default:
			ok++
			for _, l := range m.entry.Lines {
				debit += l.Debit
			}
			if verbose {
				printEntry(m.entry)
			}
		}
	}
	printCounts("Unmapped accounts (add them to \"accounts\")", unmappedAccounts)
	printCounts("Unknown VAT codes (add them to \"vat_codes\")", unmappedVAT)
	fmt.Printf("\n%d vouchers ready (%s debit total), %d empty, %d with errors\n", ok, debit, empty, failed)
	if failed > 0 {
		return fmt.Errorf("%d vouchers cannot be sent", failed)
	}
	return nil
}

func printCounts(title string, counts map[string]int) {
	if len(counts) == 0 {
		return
	}
	keys := make([]string, 0, len(counts))
	for k := range counts {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	fmt.Printf("\n%s:\n", title)
	for _, k := range keys {
		fmt.Printf("  %-8s used by %d vouchers\n", k, counts[k])
	}
}

func printEntry(e accounted.JournalEntry) {
	fmt.Printf("\n%s  %s  [%s]\n", e.EntryDate, e.Description, e.SourceID)
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', tabwriter.AlignRight)
	for _, l := range e.Lines {
		d, c := "", ""
		if l.Debit != 0 {
			d = l.Debit.String()
		}
		if l.Credit != 0 {
			c = l.Credit.String()
		}
		fmt.Fprintf(w, "  %s\t%s\t%s\t  %s\t\n", l.Account, d, c, l.Description)
	}
	w.Flush()
}

func runPush(ctx context.Context, args []string) error {
	var configPath, statePath string
	var dryRun, commit bool
	_, export, err := parseFlags("push", args, func(fs *flag.FlagSet) {
		fs.StringVar(&configPath, "config", "config.json", "mapping config")
		fs.StringVar(&statePath, "state", "multicase-state.json", "file recording what has been sent")
		fs.BoolVar(&dryRun, "dry-run", false, "let Accounted validate every voucher without saving anything")
		fs.BoolVar(&commit, "commit", false, "post the drafts and assign voucher numbers")
	})
	if err != nil {
		return err
	}
	if dryRun && commit {
		return errors.New("-dry-run and -commit cannot be combined")
	}
	apiKey, companyID := os.Getenv("ACCOUNTED_API_KEY"), os.Getenv("ACCOUNTED_COMPANY_ID")
	if apiKey == "" || companyID == "" {
		return errors.New("ACCOUNTED_API_KEY and ACCOUNTED_COMPANY_ID must be set")
	}
	baseURL := os.Getenv("ACCOUNTED_URL")
	if baseURL == "" {
		baseURL = "https://app.accounted.se"
	}

	_, items, err := load(configPath, export)
	if err != nil {
		return err
	}
	var entries []mapped
	var problems []string
	for _, m := range items {
		switch {
		case errors.Is(m.err, mapping.ErrEmpty):
		case m.err != nil:
			problems = append(problems, fmt.Sprintf("%s: %v", m.voucher.Label(), m.err))
		default:
			entries = append(entries, m)
		}
	}
	if len(problems) > 0 {
		return fmt.Errorf("nothing sent, fix the mapping first (run check):\n  %s", strings.Join(problems, "\n  "))
	}

	client := accounted.NewClient(baseURL, apiKey, companyID)
	periods, err := client.FiscalPeriods(ctx)
	if err != nil {
		return fmt.Errorf("list fiscal periods: %w", err)
	}
	for i := range entries {
		p, err := periodFor(periods, entries[i].entry.EntryDate)
		if err != nil {
			problems = append(problems, fmt.Sprintf("%s: %v", entries[i].voucher.Label(), err))
			continue
		}
		entries[i].entry.FiscalPeriodID = p.ID
	}
	if len(problems) > 0 {
		return fmt.Errorf("nothing sent:\n  %s", strings.Join(problems, "\n  "))
	}

	st, err := state.Load(statePath)
	if err != nil {
		return fmt.Errorf("load %s: %w", statePath, err)
	}

	var created, posted, skipped, warned int
	for _, m := range entries {
		if ctx.Err() != nil {
			return ctx.Err()
		}
		e := m.entry
		label := m.voucher.Label()
		hash := hashEntry(e)
		rec, seen := st.Get(companyID, e.SourceID)

		if seen && rec.Hash != hash {
			fmt.Printf("WARN  %s changed in Multicase since it was sent as %s; correct it in Accounted\n", label, describe(rec))
			warned++
			continue
		}
		if seen && (rec.Status == "posted" || !commit) {
			skipped++
			continue
		}

		if !seen {
			id, err := client.CreateDraft(ctx, e, idempotencyKey(companyID, e.SourceID, hash, "create"), dryRun)
			if err != nil {
				return fmt.Errorf("%s: %w", label, err)
			}
			if dryRun {
				fmt.Printf("OK    %s validated\n", label)
				created++
				continue
			}
			rec = state.Record{CompanyID: companyID, EntryID: id, Status: "draft", Hash: hash}
			if err := st.Put(e.SourceID, rec); err != nil {
				return err
			}
			created++
			if !commit {
				fmt.Printf("DRAFT %s -> %s\n", label, id)
				continue
			}
		}

		c, err := client.Commit(ctx, rec.EntryID, idempotencyKey(companyID, rec.EntryID, hash, "commit"))
		if err != nil {
			return fmt.Errorf("%s: commit %s: %w", label, rec.EntryID, err)
		}
		rec.Status, rec.VoucherSeries, rec.VoucherNumber = "posted", c.VoucherSeries, c.VoucherNumber
		if err := st.Put(e.SourceID, rec); err != nil {
			return err
		}
		posted++
		fmt.Printf("POST  %s -> %s%d\n", label, c.VoucherSeries, c.VoucherNumber)
	}

	verb := "drafts created"
	if dryRun {
		verb = "validated"
	}
	fmt.Printf("\n%d %s, %d posted, %d already sent, %d changed since sent\n", created, verb, posted, skipped, warned)
	return nil
}

func periodFor(periods []accounted.FiscalPeriod, date string) (accounted.FiscalPeriod, error) {
	for _, p := range periods {
		if p.PeriodStart <= date && date <= p.PeriodEnd {
			if p.IsClosed || p.LockedAt != nil {
				return p, fmt.Errorf("fiscal period %s is closed or locked", p.Name)
			}
			return p, nil
		}
	}
	return accounted.FiscalPeriod{}, fmt.Errorf("no fiscal period covers %s", date)
}

func describe(r state.Record) string {
	if r.Status == "posted" {
		return fmt.Sprintf("voucher %s%d", r.VoucherSeries, r.VoucherNumber)
	}
	return "draft " + r.EntryID
}

func hashEntry(e accounted.JournalEntry) string {
	b, _ := json.Marshal(e)
	sum := sha256.Sum256(b)
	return hex.EncodeToString(sum[:])
}

func idempotencyKey(parts ...string) string {
	sum := sha256.Sum256([]byte(strings.Join(parts, "\x00")))
	return "multicase-" + hex.EncodeToString(sum[:16])
}