# SPDX-FileCopyrightText: Amolith <amolith@secluded.site>
#
# SPDX-License-Identifier: Unlicense

# Fallback to the configured agent command (Crush by default) when a command is not found.

# Configure the prefix that marks commands for routing to the agent.
if not set -q __AGENTSH_PREFIX_CHAR
    set -g __AGENTSH_PREFIX_CHAR "✨"
end

if not set -q __AGENTSH_PREFIX
    set -g __AGENTSH_PREFIX "$__AGENTSH_PREFIX_CHAR "
end

if not set -q __AGENTSH_RUNNER
    set -g __AGENTSH_RUNNER crush run --quiet
end

set -g __AGENTSH_PREFIX_ACTIVE 0

# Preserve any previously defined handler so we can delegate if needed
if functions -q fish_command_not_found
    functions -c fish_command_not_found __agentsh_prev_fish_command_not_found
end

# Command not found handler
function fish_command_not_found
    set -l missing_command $argv[1]
    set -l remaining_args $argv[2..-1]

    # Nothing to do without a command name
    if test -z "$missing_command"
        echo "fish: command not found" >&2
        return 127
    end

    set -l prefix_char $__AGENTSH_PREFIX_CHAR
    set -l handled false
    set -l effective_cmd

    # Check if command starts with prefix
    if test "$missing_command" = "$prefix_char"
        set handled true
        set effective_cmd $remaining_args
    else if string match -q "$prefix_char*" -- "$missing_command"
        set handled true
        set -l stripped (string replace -- "$prefix_char" "" -- "$missing_command")
        if test -n "$stripped"
            set effective_cmd $stripped $remaining_args
        else
            set effective_cmd $remaining_args
        end
    end

    if test "$handled" != true
        if functions -q __agentsh_prev_fish_command_not_found
            __agentsh_prev_fish_command_not_found $argv
            return $status
        end
        echo "fish: command not found: $missing_command" >&2
        return 127
    end

    if test (count $effective_cmd) -eq 0
        echo "agentsh: nothing to run after '$prefix_char'." >&2
        return 127
    end

    if not set -q __AGENTSH_RUNNER[1]
        echo "agentsh: no runner configured; set __AGENTSH_RUNNER before sourcing agentsh." >&2
        return 127
    end

    set -l runner $__AGENTSH_RUNNER
    set -l runner_exe $runner[1]

    if not type -q -- $runner_exe
        if functions -q __agentsh_prev_fish_command_not_found
            __agentsh_prev_fish_command_not_found $argv
            return $status
        end
        echo "agentsh: $runner_exe: command not found; unable to handle '$effective_cmd[1]'." >&2
        return 127
    end

    # Build command string as single argument
    set -l full_cmd (string join ' ' -- $effective_cmd)

    $runner $full_cmd
    return $status
end

# Toggle prefix function
function __agentsh_toggle_prefix
    set -l prefix $__AGENTSH_PREFIX
    set -l prefix_len (string length -- $prefix)
    set -l buffer (commandline)
    set -l cursor_pos (commandline -C)

    if string match -q "$prefix*" -- "$buffer"
        # Remove prefix
        set -l new_buffer (string sub --start (math $prefix_len + 1) -- $buffer)
        commandline -r -- $new_buffer

        if test $cursor_pos -gt $prefix_len
            commandline -C (math $cursor_pos - $prefix_len)
        else
            commandline -C 0
        end
        set -g __AGENTSH_PREFIX_ACTIVE 0
    else
        # Add prefix
        commandline -r -- "$prefix$buffer"
        commandline -C (math $cursor_pos + $prefix_len)
        set -g __AGENTSH_PREFIX_ACTIVE 1
    end
end

# Hook to persist prefix across prompts
function __agentsh_postexec --on-event fish_postexec
    if test $__AGENTSH_PREFIX_ACTIVE -eq 1
        commandline -f repaint
    end
end

# Guard backward deletion to prevent removing prefix
function __agentsh_guard_backward_delete
    if test $__AGENTSH_PREFIX_ACTIVE -eq 0
        commandline -f backward-delete-char
        return
    end

    set -l prefix $__AGENTSH_PREFIX
    set -l prefix_len (string length -- $prefix)
    set -l buffer (commandline)
    set -l cursor_pos (commandline -C)

    # Don't delete if we're at or before the prefix boundary
    if string match -q "$prefix*" -- "$buffer"; and test $cursor_pos -le $prefix_len
        return
    end

    commandline -f backward-delete-char
end

function __agentsh_guard_backward_kill_word
    if test $__AGENTSH_PREFIX_ACTIVE -eq 0
        commandline -f backward-kill-word
        return
    end

    set -l prefix $__AGENTSH_PREFIX
    set -l prefix_len (string length -- $prefix)
    set -l buffer (commandline)
    set -l cursor_pos (commandline -C)

    if string match -q "$prefix*" -- "$buffer"; and test $cursor_pos -le $prefix_len
        return
    end

    commandline -f backward-kill-word
end

# Set up key bindings
if status is-interactive
    # Bind Ctrl+X to toggle prefix
    bind \cx __agentsh_toggle_prefix

    # Bind multiple backspace variants
    bind \b __agentsh_guard_backward_delete
    bind \x7f __agentsh_guard_backward_delete
    bind backspace __agentsh_guard_backward_delete
    
    # Bind Alt+Backspace variants
    bind \eb __agentsh_guard_backward_kill_word
    bind \e\x7f __agentsh_guard_backward_kill_word
    
    # Bind Ctrl+W
    bind \cw __agentsh_guard_backward_kill_word
    
    # Bind in insert mode too
    bind -M insert \b __agentsh_guard_backward_delete
    bind -M insert \x7f __agentsh_guard_backward_delete
    bind -M insert \eb __agentsh_guard_backward_kill_word
    bind -M insert \e\x7f __agentsh_guard_backward_kill_word
    bind -M insert \cw __agentsh_guard_backward_kill_word
end