[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

vendor/github.com/ncruces/go-sqlite3/context.go

@@ -0,0 +1,229 @@
+package sqlite3
+
+import (
+	"encoding/json"
+	"errors"
+	"math"
+	"time"
+
+	"github.com/ncruces/go-sqlite3/internal/util"
+)
+
+// Context is the context in which an SQL function executes.
+// An SQLite [Context] is in no way related to a Go [context.Context].
+//
+// https://sqlite.org/c3ref/context.html
+type Context struct {
+	c      *Conn
+	handle uint32
+}
+
+// Conn returns the database connection of the
+// [Conn.CreateFunction] or [Conn.CreateWindowFunction]
+// routines that originally registered the application defined function.
+//
+// https://sqlite.org/c3ref/context_db_handle.html
+func (ctx Context) Conn() *Conn {
+	return ctx.c
+}
+
+// SetAuxData saves metadata for argument n of the function.
+//
+// https://sqlite.org/c3ref/get_auxdata.html
+func (ctx Context) SetAuxData(n int, data any) {
+	ptr := util.AddHandle(ctx.c.ctx, data)
+	ctx.c.call("sqlite3_set_auxdata_go", uint64(ctx.handle), uint64(n), uint64(ptr))
+}
+
+// GetAuxData returns metadata for argument n of the function.
+//
+// https://sqlite.org/c3ref/get_auxdata.html
+func (ctx Context) GetAuxData(n int) any {
+	ptr := uint32(ctx.c.call("sqlite3_get_auxdata", uint64(ctx.handle), uint64(n)))
+	return util.GetHandle(ctx.c.ctx, ptr)
+}
+
+// ResultBool sets the result of the function to a bool.
+// SQLite does not have a separate boolean storage class.
+// Instead, boolean values are stored as integers 0 (false) and 1 (true).
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultBool(value bool) {
+	var i int64
+	if value {
+		i = 1
+	}
+	ctx.ResultInt64(i)
+}
+
+// ResultInt sets the result of the function to an int.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultInt(value int) {
+	ctx.ResultInt64(int64(value))
+}
+
+// ResultInt64 sets the result of the function to an int64.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultInt64(value int64) {
+	ctx.c.call("sqlite3_result_int64",
+		uint64(ctx.handle), uint64(value))
+}
+
+// ResultFloat sets the result of the function to a float64.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultFloat(value float64) {
+	ctx.c.call("sqlite3_result_double",
+		uint64(ctx.handle), math.Float64bits(value))
+}
+
+// ResultText sets the result of the function to a string.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultText(value string) {
+	ptr := ctx.c.newString(value)
+	ctx.c.call("sqlite3_result_text64",
+		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
+		uint64(ctx.c.freer), _UTF8)
+}
+
+// ResultRawText sets the text result of the function to a []byte.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultRawText(value []byte) {
+	ptr := ctx.c.newBytes(value)
+	ctx.c.call("sqlite3_result_text64",
+		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
+		uint64(ctx.c.freer), _UTF8)
+}
+
+// ResultBlob sets the result of the function to a []byte.
+// Returning a nil slice is the same as calling [Context.ResultNull].
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultBlob(value []byte) {
+	ptr := ctx.c.newBytes(value)
+	ctx.c.call("sqlite3_result_blob64",
+		uint64(ctx.handle), uint64(ptr), uint64(len(value)),
+		uint64(ctx.c.freer))
+}
+
+// ResultZeroBlob sets the result of the function to a zero-filled, length n BLOB.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultZeroBlob(n int64) {
+	ctx.c.call("sqlite3_result_zeroblob64",
+		uint64(ctx.handle), uint64(n))
+}
+
+// ResultNull sets the result of the function to NULL.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultNull() {
+	ctx.c.call("sqlite3_result_null",
+		uint64(ctx.handle))
+}
+
+// ResultTime sets the result of the function to a [time.Time].
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultTime(value time.Time, format TimeFormat) {
+	if format == TimeFormatDefault {
+		ctx.resultRFC3339Nano(value)
+		return
+	}
+	switch v := format.Encode(value).(type) {
+	case string:
+		ctx.ResultText(v)
+	case int64:
+		ctx.ResultInt64(v)
+	case float64:
+		ctx.ResultFloat(v)
+	default:
+		panic(util.AssertErr())
+	}
+}
+
+func (ctx Context) resultRFC3339Nano(value time.Time) {
+	const maxlen = uint64(len(time.RFC3339Nano)) + 5
+
+	ptr := ctx.c.new(maxlen)
+	buf := util.View(ctx.c.mod, ptr, maxlen)
+	buf = value.AppendFormat(buf[:0], time.RFC3339Nano)
+
+	ctx.c.call("sqlite3_result_text64",
+		uint64(ctx.handle), uint64(ptr), uint64(len(buf)),
+		uint64(ctx.c.freer), _UTF8)
+}
+
+// ResultPointer sets the result of the function to NULL, just like [Context.ResultNull],
+// except that it also associates ptr with that NULL value such that it can be retrieved
+// within an application-defined SQL function using [Value.Pointer].
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultPointer(ptr any) {
+	valPtr := util.AddHandle(ctx.c.ctx, ptr)
+	ctx.c.call("sqlite3_result_pointer_go", uint64(valPtr))
+}
+
+// ResultJSON sets the result of the function to the JSON encoding of value.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultJSON(value any) {
+	data, err := json.Marshal(value)
+	if err != nil {
+		ctx.ResultError(err)
+		return
+	}
+	ctx.ResultRawText(data)
+}
+
+// ResultValue sets the result of the function to a copy of [Value].
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultValue(value Value) {
+	if value.c != ctx.c {
+		ctx.ResultError(MISUSE)
+		return
+	}
+	ctx.c.call("sqlite3_result_value",
+		uint64(ctx.handle), uint64(value.handle))
+}
+
+// ResultError sets the result of the function an error.
+//
+// https://sqlite.org/c3ref/result_blob.html
+func (ctx Context) ResultError(err error) {
+	if errors.Is(err, NOMEM) {
+		ctx.c.call("sqlite3_result_error_nomem", uint64(ctx.handle))
+		return
+	}
+
+	if errors.Is(err, TOOBIG) {
+		ctx.c.call("sqlite3_result_error_toobig", uint64(ctx.handle))
+		return
+	}
+
+	msg, code := errorCode(err, _OK)
+	if msg != "" {
+		defer ctx.c.arena.mark()()
+		ptr := ctx.c.arena.string(msg)
+		ctx.c.call("sqlite3_result_error",
+			uint64(ctx.handle), uint64(ptr), uint64(len(msg)))
+	}
+	if code != _OK {
+		ctx.c.call("sqlite3_result_error_code",
+			uint64(ctx.handle), uint64(code))
+	}
+}
+
+// VTabNoChange may return true if a column is being fetched as part
+// of an update during which the column value will not change.
+//
+// https://sqlite.org/c3ref/vtab_nochange.html
+func (ctx Context) VTabNoChange() bool {
+	r := ctx.c.call("sqlite3_vtab_nochange", uint64(ctx.handle))
+	return r != 0
+}