1 files changed, 136 insertions, 0 deletions
diff --git a/duplicate_finder/output.py b/duplicate_finder/output.py
new file mode 100644
index 0000000..c3b6307
--- /dev/null
+++ b/duplicate_finder/output.py
@@ -0,0 +1,136 @@
+# SPDX-FileCopyrightText: 2026 Dennis Fink <me+coding@dennisfink.me>
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+"""Render duplicate-file groups in terminal-friendly output formats."""
+
+import shlex
+from json import dumps as json_dumps
+
+import click_extra as click
+import humanize
+from tabulate import tabulate
+
+from .types import FilesByHash
+
+OUTPUTS = {}
+
+
+def register_output(f):
+    OUTPUTS[f.__name__] = f
+    return f
+
+
+@register_output
+def human(
+    duplicates: FilesByHash, show_size: bool = False, human_readable: bool = False
+) -> None:
+    """Print duplicate groups in a human-readable format.
+
+    :param duplicates: Hash digests mapped to files sharing each digest.
+    :param show_size: Whether to display the size of each duplicate group.
+    :param human_readable: Whether displayed sizes should use human-readable units.
+    """
+    for hash_digest, files in duplicates.items():
+        click.secho("Duplicate set ", fg="green", bold=True, nl=False)
+        click.secho("[", fg="magenta", bold=True, nl=False)
+        click.secho(hash_digest, fg="cyan", bold=True, nl=False)
+        click.secho("]", fg="magenta", bold=True, nl=False)
+
+        if show_size:
+            size = next(iter(files)).size
+            click.secho(" [", fg="magenta", bold=True, nl=False)
+            click.secho(
+                humanize.naturalsize(size) if human_readable else size,
+                fg="cyan",
+                bold=True,
+                nl=False,
+            )
+            click.secho("]", fg="magenta", bold=True, nl=False)
+
+        click.secho(":", fg="green", bold=True)
+
+        for file in files:
+            click.echo(f"  {file.path}")
+
+
+@register_output
+def plain(
+    duplicates: FilesByHash, show_size: bool = False, human_readable: bool = False
+) -> None:
+    """Print duplicate groups as shell-quoted, space-separated fields.
+
+    Each duplicate group is written on a separate line. The hash digest is the
+    first field, followed by the duplicate paths. If requested, the file size is
+    appended as the final field.
+
+    :param duplicates: Hash digests mapped to files sharing each digest.
+    :param show_size: Whether to append the size of each duplicate group.
+    :param human_readable: Whether displayed sizes should use human-readable units.
+    """
+    for hash_digest, files in duplicates.items():
+        fields = [hash_digest]
+        fields.extend(str(file.path) for file in files)
+
+        if show_size:
+            size = next(iter(files)).size
+            fields.append(humanize.naturalsize(size) if human_readable else str(size))
+
+        click.echo(shlex.join(fields))
+
+
+@register_output
+def table(
+    duplicates: FilesByHash, show_size: bool = False, human_readable: bool = False
+) -> None:
+    """Print duplicate groups as a column-aligned table.
+
+    :param duplicates: Hash digests mapped to files sharing each digest.
+    :param show_size: Whether to display the size of each duplicate group.
+    :param human_readable: Whether displayed sizes should use human-readable units.
+    """
+    rows = []
+    for hash_digest, files in duplicates.items():
+        for file in files:
+            if show_size:
+                rows.append(
+                    (
+                        click.style(hash_digest, fg="cyan"),
+                        file.path,
+                        humanize.naturalsize(file.size)
+                        if human_readable
+                        else file.size,
+                    )
+                )
+            else:
+                rows.append((click.style(hash_digest, fg="cyan"), file.path))
+
+    click.echo(tabulate(rows, tablefmt="plain"))
+
+
+@register_output
+def json(
+    duplicates: FilesByHash, show_size: bool = False, human_readable: bool = False
+) -> None:
+    """Print duplicate groups as JSON.
+
+    File paths are serialized as absolute strings. ``show_size`` is accepted for
+    the common output-function interface but does not change the JSON structure.
+
+    :param duplicates: Hash digests mapped to files sharing each digest.
+    :param show_size: Unused; accepted for consistency with other output formats.
+    :param human_readable: Whether the JSON should be pretty-printed.
+    """
+    json_config = {"separators": (",", ":"), "indent": 0, "sort_keys": False}
+
+    if human_readable:
+        json_config["separators"] = (",", ": ")
+        json_config["indent"] = 2
+        json_config["sort_keys"] = True
+
+    serialized_duplicates = {
+        hash_digest: [str(file.path.absolute()) for file in files]
+        for hash_digest, files in duplicates.items()
+    }
+
+    click.echo(json_dumps(serialized_duplicates, **json_config))