1 files changed, 79 insertions, 0 deletions
diff --git a/internal/state/state.go b/internal/state/state.go
new file mode 100644
index 0000000..f530d96
--- /dev/null
+++ b/internal/state/state.go
@@ -0,0 +1,79 @@
+// Package state records which Multicase vouchers have been sent, so a
+// re-run of the same or an overlapping export does not book them twice.
+// Accounted's idempotency keys expire after 24 hours; this file does not.
+package state
+
+import (
+	"encoding/json"
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+type Record struct {
+	CompanyID     string    `json:"company_id"`
+	EntryID       string    `json:"entry_id"`
+	Status        string    `json:"status"` // "draft" or "posted"
+	VoucherSeries string    `json:"voucher_series,omitempty"`
+	VoucherNumber int       `json:"voucher_number,omitempty"`
+	Hash          string    `json:"hash"`
+	UpdatedAt     time.Time `json:"updated_at"`
+}
+
+type File struct {
+	path    string
+	Entries map[string]Record `json:"entries"`
+}
+
+func Load(path string) (*File, error) {
+	f := &File{path: path, Entries: map[string]Record{}}
+	b, err := os.ReadFile(path)
+	if errors.Is(err, fs.ErrNotExist) {
+		return f, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	if err := json.Unmarshal(b, f); err != nil {
+		return nil, err
+	}
+	if f.Entries == nil {
+		f.Entries = map[string]Record{}
+	}
+	return f, nil
+}
+
+func key(companyID, sourceID string) string {
+	return companyID + "/" + sourceID
+}
+
+func (f *File) Get(companyID, sourceID string) (Record, bool) {
+	r, ok := f.Entries[key(companyID, sourceID)]
+	return r, ok
+}
+
+// Put stores the record and writes the file, so progress survives a crash
+// halfway through a run.
+func (f *File) Put(sourceID string, r Record) error {
+	r.UpdatedAt = time.Now().UTC()
+	f.Entries[key(r.CompanyID, sourceID)] = r
+	b, err := json.MarshalIndent(f, "", "  ")
+	if err != nil {
+		return err
+	}
+	tmp, err := os.CreateTemp(filepath.Dir(f.path), ".state-*")
+	if err != nil {
+		return err
+	}
+	defer os.Remove(tmp.Name())
+	if _, err := tmp.Write(b); err != nil {
+		tmp.Close()
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+	return os.Rename(tmp.Name(), f.path)
+}