diff --git a/.gitignore b/.gitignore
index 54e7cfe..f4d9dba 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 personal_access_token
+test.csv
+collection.gob
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..4f19000
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "go-discogs"]
+	path = go-discogs
+	url = https://github.com/irlndts/go-discogs.git
diff --git a/go.mod b/go.mod
index 838794e..3f632d5 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,4 @@ module git.hrfee.pw/hrfee/discogs-pricer
 
 go 1.22.4
 
-require github.com/irlndts/go-discogs v0.3.6 // indirect
+require github.com/hrfee/go-discogs v0.0.0-20240905170225-50ee0e6a98ae // indirect
diff --git a/go.sum b/go.sum
index 3516c17..ec9e25b 100644
--- a/go.sum
+++ b/go.sum
@@ -1,2 +1,4 @@
-github.com/irlndts/go-discogs v0.3.6 h1:3oIJEkLGQ1ffJcoo6wvtawPI4/SyHoRpnu25Y51U4wg=
-github.com/irlndts/go-discogs v0.3.6/go.mod h1:UVQ05FdCzH4P/usnSxQDh77QYE37HvmPnSCgogioljo=
+github.com/google/go-cmp v0.5.6 h1:BKbKCqvP6I+rmFHt06ZmyQtvB8xAkWdhFyr0ZUNZcxQ=
+github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/hrfee/go-discogs v0.0.0-20240905170225-50ee0e6a98ae h1:9uX6ArLOVUzryMkT3VKud4c/5vNwWEwdR6vJHHvh2tw=
+github.com/hrfee/go-discogs v0.0.0-20240905170225-50ee0e6a98ae/go.mod h1:Z34PS6moBg1QdybW9LkrqciRJHKdyQ9hpxvaiH8sFic=
diff --git a/main.go b/main.go
index 691300c..6cb5f8c 100644
--- a/main.go
+++ b/main.go
@@ -1,43 +1,290 @@
 package main
 
 import (
+	"encoding/csv"
+	"encoding/gob"
+	"encoding/json"
 	"errors"
+	"flag"
 	"fmt"
 	"os"
+	"strconv"
 	"strings"
+	"time"
 
-	"github.com/irlndts/go-discogs"
+	"github.com/hrfee/go-discogs"
 )
 
 var (
 	CURRENCY   = "GBP"
 	USER_AGENT = "discogs-pricer/0.0 +https://git.hrfee.pw/hrfee/discogs-pricer"
+
+	STORE = "./collection.gob"
+
+	PER_PAGE = 75
+
+	NotesFieldID = 4 // Test, otherwise use 3
+
+	noPaToken = errors.New(`put "hrfee:<personal access token>" in ./personal_access_token and re-run.`)
 )
 
-/*type ServiceWriter interface {
-	WriteRow(svcID string, name string, price string, purchaseDate time.Time, notes string)
-}*/
+type ItemHash string
 
 type Client struct {
-	c discogs.Discogs
+	Username        string
+	c               discogs.Discogs
+	StorePath       string
+	CollectionCache struct {
+		Items map[ItemHash]CollectionItem // Hash of a load of IDs to Collection Item
+		Order []ItemHash
+	}
 }
 
-func NewClient(currency string, userAgent string, token string) (*Client, error) {
-	client := Client{}
+func NewClient(currency string, userAgent string, username, token string, storePath string) (*Client, error) {
+	client := Client{Username: username, StorePath: storePath}
 	var err error
 	client.c, err = discogs.New(&discogs.Options{
 		UserAgent: userAgent,
 		Currency:  currency,
 		Token:     token,
+		// URL:       "http://localhost:8097",
 	})
+	if err == nil {
+		client.ClearCollectionCache()
+		err = client.ReadCollectionCache()
+	}
 	return &client, err
 }
 
-func main() {
-	token, err := os.ReadFile("personal_access_token")
+// Items, error, and whether or not there's more pages to go.
+func (c *Client) collection(pageNo int, allocate bool) ([]discogs.CollectionItemSource, error, bool) {
+	fmt.Printf("Getting collection page %d for user %s\n", pageNo, c.Username)
+	cf, err := c.c.CollectionItemsByFolder(c.Username, 0, &discogs.Pagination{
+		Sort:      "added",
+		SortOrder: "asc",
+		Page:      pageNo,
+		PerPage:   PER_PAGE,
+	})
 	if err != nil {
-		panic(errors.New("no token found in ./personal_access_token"))
+		return []discogs.CollectionItemSource{}, err, false
 	}
-	c, err := NewClient(CURRENCY, USER_AGENT, strings.TrimSuffix(string(token), "\n"))
-	fmt.Println("vim-go")
+	if allocate {
+		c.CollectionCache.Order = make([]ItemHash, 0, cf.Pagination.Pages*PER_PAGE)
+	}
+	return cf.Items, err, cf.Pagination.Page < cf.Pagination.Pages
+}
+
+func (c *Client) ClearCollectionCache() {
+	c.CollectionCache.Order = []ItemHash{}
+	c.CollectionCache.Items = map[ItemHash]CollectionItem{}
+}
+
+func (c *Client) PopulateCollectionCache() error {
+	more := true
+	var err error
+	var p []discogs.CollectionItemSource
+	i := 0
+	for more {
+		p, err, more = c.collection(i, i == 0)
+		if err != nil {
+			return err
+		}
+		for i := range p {
+			ci := CollectionItem{p[i]}
+			hash := ci.Hash()
+			if _, ok := c.CollectionCache.Items[hash]; ok {
+				continue
+			}
+			c.CollectionCache.Order = append(c.CollectionCache.Order, hash)
+			c.CollectionCache.Items[hash] = ci
+		}
+		i++
+	}
+	return c.StoreCollectionCache()
+}
+
+func (c *Client) StoreCollectionCache() error {
+	file, err := os.Create(c.StorePath)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	enc := gob.NewEncoder(file)
+	return enc.Encode(c.CollectionCache)
+}
+
+func (c *Client) ReadCollectionCache() error {
+	file, err := os.Open(c.StorePath)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return nil
+		}
+		return err
+	}
+	defer file.Close()
+	dec := gob.NewDecoder(file)
+	return dec.Decode(&c.CollectionCache)
+}
+
+func (c *Client) CollectionJSON() (string, error) {
+	if c.CollectionCache.Order == nil || len(c.CollectionCache.Order) == 0 {
+		if err := c.PopulateCollectionCache(); err != nil {
+			return "", err
+		}
+		if err := c.StoreCollectionCache(); err != nil {
+			return "", err
+		}
+	}
+
+	v, _ := json.MarshalIndent(c.CollectionCache.Items, "", "\t")
+	return string(v), nil
+}
+
+func (c *Client) WriteCSVTemplate(path string) error {
+	if c.CollectionCache.Order == nil || len(c.CollectionCache.Order) == 0 {
+		if err := c.PopulateCollectionCache(); err != nil {
+			return err
+		}
+		if err := c.StoreCollectionCache(); err != nil {
+			return err
+		}
+	}
+	file, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+	w := csv.NewWriter(file)
+	w.Write(HeaderRow)
+	for _, ciHash := range c.CollectionCache.Order {
+		w.Write(c.CollectionCache.Items[ciHash].RowFromCollectionItem())
+	}
+	return nil
+}
+
+func (c *Client) TestEditField() {
+	err := c.c.EditFieldsInstance(c.Username, 1, 10191384, 313879623, discogs.NotesField, "a new 2nd value!")
+	fmt.Printf("Error: %v\n", err)
+}
+
+var HeaderRow = strings.Split(
+	"Folder ID,Release ID,Instance ID,Artist - Name,Date Added,Price,Purchased Date,Additional Notes",
+	",",
+)
+
+type CollectionItem struct {
+	discogs.CollectionItemSource
+}
+
+// Not a real hash, but identifies a record uniquely enough.
+func (ci CollectionItem) Hash() ItemHash {
+	return ItemHash(strconv.Itoa(ci.ID) + "|" + strconv.Itoa(ci.InstanceID))
+}
+
+func ParseTime(t string) (time.Time, error) {
+	return time.Parse("2006-01-02T15:04:05-07:00", t)
+}
+
+func (ci CollectionItem) RawNotes() string {
+	notes := ""
+	for _, n := range ci.Notes {
+		if n.FieldID == discogs.NotesField {
+			notes = n.Value
+		}
+	}
+	return notes
+}
+
+type ParsedNotes struct {
+	Price        string
+	PurchaseDate time.Time
+	Additional   string
+}
+
+func (ci CollectionItem) ParseNotes() ParsedNotes {
+	notes := ci.RawNotes()
+	pn := ParsedNotes{}
+	dateString := ""
+	n, err := fmt.Sscanf(notes, "Purchase Price: %s, Purchase Date: %s.%s", &(pn.Price), &dateString, &(pn.Additional))
+	if n <= 0 || err != nil {
+		pn.Additional = notes
+	}
+	pn.PurchaseDate, err = time.Parse("2006-01-02", dateString)
+	if err != nil || dateString == "" || pn.PurchaseDate.IsZero() {
+		pn.PurchaseDate, _ = ParseTime(ci.DateAdded)
+	}
+	return pn
+}
+
+func (ci CollectionItem) RowFromCollectionItem() []string {
+	dateAdded, err := ParseTime(ci.DateAdded)
+	if err != nil {
+		panic(err)
+	}
+	notes := ci.ParseNotes()
+	row := []string{
+		strconv.Itoa(ci.FolderID),
+		strconv.Itoa(ci.ID),
+		strconv.Itoa(ci.InstanceID),
+		ci.BasicInformation.Artists[0].Name + " - " + ci.BasicInformation.Title,
+		dateAdded.Format("2006-01-02"),
+		notes.Price,
+		notes.PurchaseDate.Format("2006-01-02"),
+		notes.Additional,
+	}
+	return row
+}
+
+func main() {
+	patContent, err := os.ReadFile("personal_access_token")
+	if err != nil {
+		panic(noPaToken)
+	}
+	userAndToken := strings.Split(string(patContent), ":")
+	if len(userAndToken) != 2 {
+		panic(noPaToken)
+	}
+
+	c, err := NewClient(CURRENCY, USER_AGENT, userAndToken[0], strings.TrimSuffix(string(userAndToken[1]), "\n"), STORE)
+	if err != nil {
+		panic(err)
+	}
+
+	reloadCollection := false
+	printCollection := false
+	csvTemplatePath := ""
+	flag.BoolVar(&reloadCollection, "reload", false, "pass to force reload of collection cache.")
+	flag.BoolVar(&printCollection, "print", false, "pass to print JSON representation of collection.")
+	flag.StringVar(&csvTemplatePath, "template", "", "filepath to write template csv to.")
+
+	flag.Parse()
+
+	args := false
+	flag.Visit(func(*flag.Flag) { args = true })
+	if !args {
+		flag.Usage()
+	}
+
+	if reloadCollection {
+		c.ClearCollectionCache()
+		if err := c.PopulateCollectionCache(); err != nil {
+			panic(err)
+		}
+	}
+
+	if printCollection {
+		v, err := c.CollectionJSON()
+		if err != nil {
+			panic(err)
+		}
+		fmt.Println(v)
+	}
+
+	if csvTemplatePath != "" {
+		if err := c.WriteCSVTemplate(csvTemplatePath); err != nil {
+			panic(err)
+		}
+	}
+
+	// c.TestEditField()
 }