wip

26 files changed, 753 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..f841105
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,46 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### Kotlin ###
+.kotlin
+.idea
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
\ No newline at end of file
diff --git a/build.gradle.kts b/build.gradle.kts
new file mode 100644
index 0000000..07e279f
--- /dev/null
+++ b/build.gradle.kts
@@ -0,0 +1,18 @@
+plugins {
+	`java-library`
+}
+allprojects {
+	group = "moe.nea"
+	version = "1.0-SNAPSHOT"
+
+	repositories {
+		mavenCentral()
+	}
+}
+dependencies {
+	api("org.jspecify:jspecify:1.0.0")
+}
+
+tasks.test {
+	useJUnitPlatform()
+}
\ No newline at end of file
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 0000000..7fc6f1f
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1 @@
+kotlin.code.style=official
diff --git a/gradle/wrapper/gradle-wrapper.jar b/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 0000000..249e583
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.jar
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 0000000..66bbdcc
--- /dev/null
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,6 @@
+#Wed Nov 13 19:50:30 CET 2024
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.8-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/gradlew b/gradlew
new file mode 100755
index 0000000..1b6c787
--- /dev/null
+++ b/gradlew
@@ -0,0 +1,234 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+
+APP_NAME="Gradle"
+APP_BASE_NAME=${0##*/}
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+# Collect all arguments for the java command;
+#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+#     shell script including quotes and variable substitutions, so put them in
+#     double quotes to make sure that they get re-expanded; and
+#   * put everything else in single quotes, so that it's not re-expanded.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/gradlew.bat b/gradlew.bat
new file mode 100644
index 0000000..107acd3
--- /dev/null
+++ b/gradlew.bat
@@ -0,0 +1,89 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%" == "" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%" == "" set DIRNAME=.
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if "%ERRORLEVEL%" == "0" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo.
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME%
+echo.
+echo Please set the JAVA_HOME variable in your environment to match the
+echo location of your Java installation.
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if "%ERRORLEVEL%"=="0" goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+exit /b 1
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/gson/build.gradle.kts b/gson/build.gradle.kts
new file mode 100644
index 0000000..0101fe4
--- /dev/null
+++ b/gson/build.gradle.kts
@@ -0,0 +1,7 @@
+plugins {
+	`java-library`
+}
+dependencies {
+	api(project(":"))
+	api("com.google.code.gson:gson:2.11.0")
+}
\ No newline at end of file
diff --git a/gson/src/main/java/moe/nea/jcp/gson/GsonOperations.java b/gson/src/main/java/moe/nea/jcp/gson/GsonOperations.java
new file mode 100644
index 0000000..7d81b9f
--- /dev/null
+++ b/gson/src/main/java/moe/nea/jcp/gson/GsonOperations.java
@@ -0,0 +1,75 @@
+package moe.nea.jcp.gson;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonNull;
+import moe.nea.pcj.JsonLikeError;
+import moe.nea.pcj.JsonLikeOperations;
+import moe.nea.pcj.ListBuilder;
+import moe.nea.pcj.ListView;
+import moe.nea.pcj.RecordBuilder;
+import moe.nea.pcj.RecordView;
+import moe.nea.pcj.Result;
+import moe.nea.pcj.Unit;
+
+public class GsonOperations implements JsonLikeOperations<JsonElement> {
+	@Override
+	public JsonElement createNull(Unit value) {
+		return JsonNull.INSTANCE;
+	}
+
+	@Override
+	public Result<Unit, ? extends JsonLikeError> getNull(JsonElement element) {
+		if (element.isJsonNull()) return Result.ok(Unit.INSTANCE);
+		return Result.fail();
+	}
+
+	@Override
+	public JsonElement createNumeric(Number value) {
+		return null;
+	}
+
+	@Override
+	public Result<Number, ? extends JsonLikeError> getInt(JsonElement element) {
+		return null;
+	}
+
+	@Override
+	public JsonElement createString(String value) {
+		return null;
+	}
+
+	@Override
+	public Result<String, ? extends JsonLikeError> getString(JsonElement element) {
+		return null;
+	}
+
+	@Override
+	public JsonElement createBoolean(boolean value) {
+		return null;
+	}
+
+	@Override
+	public Result<Boolean, ? extends JsonLikeError> getBoolean(JsonElement jsonElement) {
+		return null;
+	}
+
+	@Override
+	public RecordBuilder<? extends JsonElement, JsonElement> createObject() {
+		return null;
+	}
+
+	@Override
+	public Result<RecordView<? extends JsonElement>, ? extends JsonLikeError> getObject(JsonElement jsonElement) {
+		return null;
+	}
+
+	@Override
+	public ListBuilder<? extends JsonElement, JsonElement> createList() {
+		return null;
+	}
+
+	@Override
+	public Result<ListView<? extends JsonElement>, ? extends JsonLikeError> getList(JsonElement jsonElement) {
+		return null;
+	}
+}
diff --git a/gson/src/main/java/moe/nea/jcp/gson/package-info.java b/gson/src/main/java/moe/nea/jcp/gson/package-info.java
new file mode 100644
index 0000000..f6947c5
--- /dev/null
+++ b/gson/src/main/java/moe/nea/jcp/gson/package-info.java
@@ -0,0 +1,4 @@
+@NullMarked
+package moe.nea.jcp.gson;
+
+import org.jspecify.annotations.NullMarked;
\ No newline at end of file
diff --git a/settings.gradle.kts b/settings.gradle.kts
new file mode 100644
index 0000000..64a6147
--- /dev/null
+++ b/settings.gradle.kts
@@ -0,0 +1,5 @@
+plugins {
+	id("org.gradle.toolchains.foojay-resolver-convention") version "0.8.0"
+}
+rootProject.name = "profunctor-codecs-java"
+include("gson")
diff --git a/src/main/java/moe/nea/pcj/AppendableError.java b/src/main/java/moe/nea/pcj/AppendableError.java
new file mode 100644
index 0000000..6ec48fa
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/AppendableError.java
@@ -0,0 +1,21 @@
+package moe.nea.pcj;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface AppendableError<T extends AppendableError<T>> {
+	/**
+	 * @return an optional Self with getSuppressed containing the argument
+	 */
+	Optional<T> appendError(Object other);
+
+	List<T> getSuppressed();
+
+	static <T> T concatError(T left, T right) {
+		if (left instanceof AppendableError<?> appendable) {
+			var opt = (Optional<T>) appendable.appendError(right);
+			return opt.orElse(left);
+		}
+		return left;
+	}
+}
diff --git a/src/main/java/moe/nea/pcj/Codec.java b/src/main/java/moe/nea/pcj/Codec.java
new file mode 100644
index 0000000..728fbc6
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Codec.java
@@ -0,0 +1,5 @@
+package moe.nea.pcj;
+
+public interface Codec<Typ, Format, DeErr, CoErr> extends Decode<Typ, Format, DeErr>, Encode<Typ, Format, CoErr> {
+
+}
diff --git a/src/main/java/moe/nea/pcj/Decode.java b/src/main/java/moe/nea/pcj/Decode.java
new file mode 100644
index 0000000..a335849
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Decode.java
@@ -0,0 +1,5 @@
+package moe.nea.pcj;
+
+public interface Decode<Typ, Format, Err> {
+	Result<Typ, Err> decode(Format format, Operation<Format> op);
+}
diff --git a/src/main/java/moe/nea/pcj/Encode.java b/src/main/java/moe/nea/pcj/Encode.java
new file mode 100644
index 0000000..0c17097
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Encode.java
@@ -0,0 +1,5 @@
+package moe.nea.pcj;
+
+public interface Encode<Typ, Format, Err> {
+	Result<Format, Err> encode(Typ data, Operation<Format> op);
+}
diff --git a/src/main/java/moe/nea/pcj/JsonLikeError.java b/src/main/java/moe/nea/pcj/JsonLikeError.java
new file mode 100644
index 0000000..6d309ab
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/JsonLikeError.java
@@ -0,0 +1,29 @@
+package moe.nea.pcj;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+public abstract class JsonLikeError<Self extends JsonLikeError<?>> implements AppendableError<JsonLikeError<?>> {
+	private final List<JsonLikeError<?>> suppressed = new ArrayList<>();
+
+	protected abstract Self copySelfWithoutSuppressions();
+
+	@Override
+	public List<JsonLikeError<?>> getSuppressed() {
+		return Collections.unmodifiableList(suppressed);
+	}
+
+	@Override
+	public Optional<JsonLikeError<?>> appendError(Object other) {
+		if (other instanceof JsonLikeError<?> jsonLikeOther) {
+			var newSelf = (JsonLikeError<?>) copySelfWithoutSuppressions();
+			newSelf.suppressed.add(jsonLikeOther.copySelfWithoutSuppressions());
+			newSelf.suppressed.addAll(jsonLikeOther.getSuppressed());
+			return Optional.of(newSelf);
+		} else {
+			return Optional.empty();
+		}
+	}
+}
diff --git a/src/main/java/moe/nea/pcj/JsonLikeOperations.java b/src/main/java/moe/nea/pcj/JsonLikeOperations.java
new file mode 100644
index 0000000..2188568
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/JsonLikeOperations.java
@@ -0,0 +1,28 @@
+package moe.nea.pcj;
+
+public interface JsonLikeOperations<Format> extends Operation<Format> {
+
+	Format createNull(Unit value);
+
+	Result<Unit, ? extends JsonLikeError> getNull(Format element);
+
+	Format createNumeric(Number value);
+
+	Result<Number, ? extends JsonLikeError> getInt(Format element);
+
+	Format createString(String value);
+
+	Result<String, ? extends JsonLikeError> getString(Format element);
+
+	Format createBoolean(boolean value);
+
+	Result<Boolean, ? extends JsonLikeError> getBoolean(Format format);
+
+	RecordBuilder<? extends Format, Format> createObject();
+
+	Result<RecordView<? extends Format>, ? extends JsonLikeError> getObject(Format format);
+
+	ListBuilder<? extends Format, Format> createList();
+
+	Result<ListView<? extends Format>, ? extends JsonLikeError> getList(Format format);
+}
diff --git a/src/main/java/moe/nea/pcj/ListBuilder.java b/src/main/java/moe/nea/pcj/ListBuilder.java
new file mode 100644
index 0000000..9f6e9a3
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/ListBuilder.java
@@ -0,0 +1,9 @@
+package moe.nea.pcj;
+
+public interface ListBuilder<Format, ElementFormat> extends ListView<ElementFormat> {
+	Format complete();
+
+	void add(ElementFormat value);
+
+	void set(int index, ElementFormat value);
+}
diff --git a/src/main/java/moe/nea/pcj/ListView.java b/src/main/java/moe/nea/pcj/ListView.java
new file mode 100644
index 0000000..57c229a
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/ListView.java
@@ -0,0 +1,14 @@
+package moe.nea.pcj;
+
+import java.util.Optional;
+
+public interface ListView<Format> {
+	int length();
+
+	default Optional<Format> getSafe(int index) {
+		if (index < 0 || index >= length()) return Optional.empty();
+		return Optional.of(getUnsafe(index));
+	}
+
+	Format getUnsafe(int index);
+}
diff --git a/src/main/java/moe/nea/pcj/Operation.java b/src/main/java/moe/nea/pcj/Operation.java
new file mode 100644
index 0000000..90995ef
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Operation.java
@@ -0,0 +1,4 @@
+package moe.nea.pcj;
+
+public interface Operation<Format> {
+}
diff --git a/src/main/java/moe/nea/pcj/RecordBuilder.java b/src/main/java/moe/nea/pcj/RecordBuilder.java
new file mode 100644
index 0000000..c28be7b
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/RecordBuilder.java
@@ -0,0 +1,6 @@
+package moe.nea.pcj;
+
+public interface RecordBuilder<Format, ElementFormat> extends RecordView<ElementFormat> {
+	void add(String key, ElementFormat value); // TODO
+	Format complete();
+}
diff --git a/src/main/java/moe/nea/pcj/RecordView.java b/src/main/java/moe/nea/pcj/RecordView.java
new file mode 100644
index 0000000..84057ba
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/RecordView.java
@@ -0,0 +1,10 @@
+package moe.nea.pcj;
+
+import java.util.Collection;
+import java.util.Optional;
+
+public interface RecordView<Format> {
+	Collection<Format> getKeys();
+
+	Optional<Format> get(String key);
+}
diff --git a/src/main/java/moe/nea/pcj/Result.java b/src/main/java/moe/nea/pcj/Result.java
new file mode 100644
index 0000000..8bec96a
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Result.java
@@ -0,0 +1,107 @@
+package moe.nea.pcj;
+
+import org.jspecify.annotations.Nullable;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+public sealed interface Result<Good, Bad> permits Result.Ok, Result.Fail {
+	default boolean isOk() {
+		return error().isEmpty();
+	}
+
+	Optional<Good> value();
+
+	Optional<Good> partial();
+
+	default Optional<Good> valueOrPartial() {
+		return value().or(this::partial);
+	}
+
+	Optional<Bad> error();
+
+	default <Next> Result<Next, Bad> map(Function<Good, Next> mapper) {
+		return flatMap(mapper.andThen(Result::ok));
+	}
+
+	default <Next> Result<Next, Bad> flatMap(Function<Good, Result<Next, Bad>> mapper) {
+		return flatMapBoth(mapper, Result::fail);
+	}
+
+	<NextGood> Result<NextGood, Bad> flatMapBoth(
+			Function<Good, Result<NextGood, Bad>> mapGood,
+			Function<Bad, Result<NextGood, Bad>> mapBad);
+
+	Result<Good, Bad> appendError(Bad error);
+
+	record Ok<Good, Bad>(Good okValue) implements Result<Good, Bad> {
+		@Override
+		public Result<Good, Bad> appendError(Bad error) {
+			return Result.partial(okValue, error);
+		}
+
+		@Override
+		public Optional<Good> partial() {
+			return Optional.empty();
+		}
+
+		@Override
+		public Optional<Good> value() {
+			return Optional.of(okValue);
+		}
+
+		@Override
+		public Optional<Bad> error() {
+			return Optional.empty();
+		}
+
+		@Override
+		public <NextGood> Result<NextGood, Bad> flatMapBoth(Function<Good, Result<NextGood, Bad>> mapGood, Function<Bad, Result<NextGood, Bad>> mapBad) {
+			return mapGood.apply(okValue);
+		}
+	}
+
+	record Fail<Good, Bad>(@Nullable Good partialValue, Bad badValue) implements Result<Good, Bad> {
+
+		@Override
+		public Optional<Good> value() {
+			return Optional.empty();
+		}
+
+		@Override
+		public Optional<Good> partial() {
+			return Optional.ofNullable(partialValue);
+		}
+
+		@Override
+		public Optional<Bad> error() {
+			return Optional.of(badValue);
+		}
+
+		@Override
+		public <NextGood> Result<NextGood, Bad> flatMapBoth(Function<Good, Result<NextGood, Bad>> mapGood, Function<Bad, Result<NextGood, Bad>> mapBad) {
+			if (partialValue != null) {
+				var nextPartial = mapGood.apply(partialValue);
+				return nextPartial.appendError(badValue);
+			}
+			return mapBad.apply(badValue);
+		}
+
+		@Override
+		public Result<Good, Bad> appendError(Bad error) {
+			return Result.partial(partialValue, AppendableError.concatError(badValue, error));
+		}
+	}
+
+	static <Good, Bad> Result<Good, Bad> ok(Good value) {
+		return new Ok<>(value);
+	}
+
+	static <Good, Bad> Result.Fail<Good, Bad> fail(Bad error) {
+		return new Fail<>(null, error);
+	}
+
+	static <Good, Bad> Result.Fail<Good, Bad> partial(@Nullable Good partial, Bad error) {
+		return new Fail<>(partial, error);
+	}
+}
diff --git a/src/main/java/moe/nea/pcj/Tuple.java b/src/main/java/moe/nea/pcj/Tuple.java
new file mode 100644
index 0000000..baaceef
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Tuple.java
@@ -0,0 +1,16 @@
+package moe.nea.pcj;
+
+public interface Tuple {
+	record Tuple2<A, B>(A first, B second) implements Tuple {}
+
+	record Tuple3<A, B, C>(A first, B second, C third) implements Tuple {}
+
+	record Tuple4<A, B, C, D>(A first, B second, C third, D fourth) implements Tuple {}
+
+	record Tuple5<A, B, C, D, E>(A first, B second, C third, D fourth, E fifth) implements Tuple {}
+
+	record Tuple6<A, B, C, D, E, F>(A first, B second, C third, D fourth, E fifth, F sixth) implements Tuple {}
+
+	record Tuple7<A, B, C, D, E, F, G>(A first, B second, C third, D fourth, E fifth, F sixth,
+	                                   G seventh) implements Tuple {}
+}
diff --git a/src/main/java/moe/nea/pcj/Unit.java b/src/main/java/moe/nea/pcj/Unit.java
new file mode 100644
index 0000000..435d763
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/Unit.java
@@ -0,0 +1,5 @@
+package moe.nea.pcj;
+
+public enum Unit {
+	INSTANCE;
+}
diff --git a/src/main/java/moe/nea/pcj/package-info.java b/src/main/java/moe/nea/pcj/package-info.java
new file mode 100644
index 0000000..8adfc56
--- /dev/null
+++ b/src/main/java/moe/nea/pcj/package-info.java
@@ -0,0 +1,4 @@
+@NullMarked
+package moe.nea.pcj;
+
+import org.jspecify.annotations.NullMarked;
\ No newline at end of file