#!/bin/sh
# fx: automates f()'s "enter a fix" prompt by gathering candidate fixes
# from a directory of pluggable sources and letting you pick one (or
# auto-picking the top one) before piping it into f's stdin.
#
# Zero changes to f.sh: this only decides what gets typed at the
# "[LEARN] ... Enter a fix" prompt, using the stdin f() already reads.
#
# Usage:
#   . src/f.sh
#   . contrib/fx/fx.sh
#   fx some-command --that --might --fail
#
# Env vars:
#   FX_SOURCES_DIR   the sources directory. Defaults to ./contrib/fx/sources.d
#                    (i.e. source this file from the repo root). There is no
#                    portable way for a *sourced* POSIX shell file to learn
#                    its own path -- $0 is the enclosing shell's name, and
#                    bash's BASH_SOURCE has no equivalent in dash/ash, so
#                    this does not try to be clever about it. Anything
#                    other than "source from repo root" (a different cwd,
#                    a temp dir a la bootstrap.sh) must set this explicitly
#                    *before* sourcing this file.
#   FX_AUTO          if set, auto-pick the top candidate instead of
#                    showing a picker
#   FX_NO_PROBE      if set, skip fx's own diagnostic run of the command
#                    (cheaper, but the 30-selfdiag.sh source gets no
#                    output to read and will have no opinion)
#
# Source contract (see sources.d/*.sh):
#   - any executable file in $FX_SOURCES_DIR
#   - invoked as:  sourcefile "$CMD"
#   - may read $FX_OUTPUT (captured stdout+stderr of one real attempt,
#     empty if FX_NO_PROBE was set)
#   - prints zero or more candidate fix lines to stdout, one per line
#   - non-zero exit or no output = "no opinion", silently skipped
#   - filename prefix (NN-name) sets display/consideration order
#
# Adding a source: drop a new executable file in sources.d/ that follows
# the contract above. Nothing else to register or edit.

# Resolved to an absolute path *now*, at source time -- a relative
# default would silently re-resolve against whatever cwd happens to be
# active later when fx() is actually called, which is almost never the
# repo root in practice.
FX_SOURCES_DIR="${FX_SOURCES_DIR:-$(pwd)/contrib/fx/sources.d}"

fx() {
    if [ ! -d "$FX_SOURCES_DIR" ]; then
        echo "fx: FX_SOURCES_DIR '$FX_SOURCES_DIR' not found -- no sources will fire." >&2
        echo "fx: set FX_SOURCES_DIR before sourcing fx.sh if not running from the repo root." >&2
    fi
    cmd="$*"

    FX_OUTPUT=""
    if [ -z "$FX_NO_PROBE" ]; then
        FX_OUTPUT=$("$@" 2>&1)
        if [ $? -eq 0 ]; then
            printf '%s\n' "$FX_OUTPUT"
            return 0
        fi
    fi
    export FX_OUTPUT

    candidates=$(
        for src in "$FX_SOURCES_DIR"/*; do
            [ -x "$src" ] || continue
            label="${src##*/}"
            "$src" "$cmd" 2>/dev/null | while IFS= read -r line; do
                [ -n "$line" ] && printf '[%s] %s\n' "$label" "$line"
            done
        done | awk -F'] ' '!seen[$2]++'
    )

    chosen=""
    if [ -n "$candidates" ]; then
        if [ -n "$FX_AUTO" ]; then
            chosen=$(printf '%s\n' "$candidates" | head -1 | sed 's/^\[[^]]*\] //')
        elif command -v fzf >/dev/null 2>&1; then
            chosen=$(printf '%s\n' "$candidates" | fzf --prompt="fix for: $cmd > " --height=40% | sed 's/^\[[^]]*\] //')
        else
            i=0
            printf '%s\n' "$candidates" | while IFS= read -r line; do
                i=$((i+1)); printf '%d) %s\n' "$i" "$line"
            done
            printf 'pick a number (blank to type your own): '
            read -r n
            [ -n "$n" ] && chosen=$(printf '%s\n' "$candidates" | sed -n "${n}p" | sed 's/^\[[^]]*\] //')
        fi
    fi

    printf '%s\n' "$chosen" | f "$@"
}