#!/usr/bin/env bash
#
# std.sh — shared "standard library" for the fastwc benchmark scripts.
#
# Provides the helpers every benchmark script needs:
#   checkfastwc()      verify a release build of fastwc exists
#   checkwc()          locate the coreutils or busybox wc implementation
#   createrandstr()    print one random 10-character alphanumeric string
#   createtxt()        create (or reuse) a text file with N such lines
#   run_benchmark_suite()  run every word/line case for the selected wc
#
# Source this file from a benchmark script, then:
#   checkfastwc
#   checkwc coreutils          # or: checkwc busybox
#   BENCH_NAME="coreutils"
#   run_benchmark_suite
#
# The suite fails fast: the moment fastwc is slower than (or disagrees
# with) the selected wc implementation, it writes a human readable report
# to FAILED-benchmark.txt and returns non-zero.

set -u

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
FASTWC="$SCRIPT_DIR/../bin/release/fastwc"
DATA_DIR="$SCRIPT_DIR/.data"
GENFILE="$SCRIPT_DIR/tools/genfile"   # optional C helper, built by test-all.sh

BENCH_NAME="${BENCH_NAME:-wc}"        # set by the caller: coreutils | busybox
BENCH_REPS="${BENCH_REPS:-3}"         # interleaved runs per case; minimum is kept
RESULT_ROWS=""                        # accumulated results table

WC_CMD=()                             # filled by checkwc(), e.g. (wc) or (busybox wc)
TEXT_FILE=""                          # filled by createtxt()

if [[ -z "$BENCH_REPS" || "$BENCH_REPS" -lt 1 ]]; then
    BENCH_REPS=1
fi

# checkfastwc — make sure ../bin/release/fastwc exists and is executable.
# Mimics autotools configure: prints "checking for ... yes/no" and bails
# out with a helpful message when the release build is missing.
checkfastwc() {
    printf 'checking for release build fastwc... '
    if [[ -x "$FASTWC" ]]; then
        printf 'yes\n'
        return 0
    fi
    printf 'no\n'
    printf 'configure: error: no release build of fastwc found at %s\n' "$FASTWC" >&2
    printf 'configure: error: run "make release" first to generate one\n' >&2
    exit 1
}

# checkwc <coreutils|busybox> — locate the requested wc implementation and
# store its invocation in $WC_CMD. Mimics autotools configure output and
# exits on failure.
checkwc() {
    local impl="$1"
    case "$impl" in
        coreutils)
            printf 'checking for coreutils wc... '
            if command -v wc >/dev/null 2>&1 \
               && wc --version 2>/dev/null | head -n1 | grep -qi 'GNU coreutils'; then
                printf 'yes\n'
                WC_CMD=(wc)
            else
                printf 'no\n'
                printf 'configure: error: GNU Coreutils wc not found in PATH\n' >&2
                exit 1
            fi
            ;;
        busybox)
            printf 'checking for busybox wc... '
            if command -v busybox >/dev/null 2>&1 \
               && busybox --list 2>/dev/null | grep -qx 'wc'; then
                printf 'yes\n'
                WC_CMD=(busybox wc)
            else
                printf 'no\n'
                printf 'configure: error: busybox (with the wc applet) not found in PATH\n' >&2
                exit 1
            fi
            ;;
        *)
            printf 'checkwc: error: unknown implementation "%s" (expected coreutils or busybox)\n' "$impl" >&2
            exit 1
            ;;
    esac
}

# createrandstr — print one 10-character random alphanumeric combination.
createrandstr() {
    local chars='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'
    local out='' i
    for ((i = 0; i < 10; i++)); do
        out+="${chars:$((RANDOM % ${#chars})):1}"
    done
    printf '%s\n' "$out"
}

# createtxt <lines> — make sure a text file with <lines> rows of random
# 10-character alphanumeric strings exists. A copy generated by a previous
# run is reused (checked by exact byte size: 10 chars + '\n' per line), so
# repeated benchmark runs are cheap. Prints the path and sets $TEXT_FILE.
createtxt() {
    local lines="$1"
    local expect=$((lines * 11))
    local have=0

    TEXT_FILE="$DATA_DIR/words-$lines.txt"

    if [[ -f "$TEXT_FILE" ]]; then
        have=$(stat -c '%s' "$TEXT_FILE" 2>/dev/null || printf '0')
    fi

    if [[ "$have" -ne "$expect" ]]; then
        mkdir -p "$DATA_DIR"
        if [[ -x "$GENFILE" ]]; then
            "$GENFILE" "$lines" > "$TEXT_FILE" || {
                printf 'createtxt: error: failed to generate %s\n' "$TEXT_FILE" >&2
                return 1
            }
        else
            printf 'createtxt: warning: %s not built, using slow shell fallback\n' "$GENFILE" >&2
            printf 'createtxt: warning: run ./test-all.sh to build the helper tools\n' >&2
            : > "$TEXT_FILE"
            for ((i = 0; i < lines; i++)); do
                createrandstr >> "$TEXT_FILE"
            done
        fi
    fi

    printf '%s\n' "$TEXT_FILE"
}

# time_ms <cmd...> — run a command once and print elapsed wall time in ms.
time_ms() {
    local s e
    s=$(date +%s%N)
    "$@" >/dev/null 2>&1
    e=$(date +%s%N)
    printf '%s\n' "$(( (e - s) / 1000000 ))"
}

# capture_count <cmd...> — print the first whitespace-separated field of a
# command's output, i.e. the count reported by `wc -w/-l` or `fastwc -w/-l`.
capture_count() {
    "$@" 2>/dev/null | awk 'NR == 1 { print $1 }'
}

# write_failed_report <label> <reason> <wc_ms> <fast_ms> — write the
# human readable failure report to FAILED-benchmark.txt.
write_failed_report() {
    local label="$1" reason="$2" wc_ms="$3" fast_ms="$4"
    local report="$SCRIPT_DIR/FAILED-benchmark.txt"

    {
        printf 'fastwc benchmark FAILED\n'
        printf '=======================\n'
        printf 'implementation : %s wc\n' "$BENCH_NAME"
        printf 'failed test    : %s\n' "$label"
        printf 'failure        : %s\n' "$reason"
        printf '\nresults\n'
        printf '%s\n' '-------'
        printf '%-28s %10s %10s %8s %s\n' 'test' 'wc' 'fastwc' 'ratio' 'status'
        printf '%s' "$RESULT_ROWS"
        printf '\nfastwc must never be slower than %s wc — benchmark aborted.\n' "$BENCH_NAME"
    } > "$report"

    printf '\nbenchmark FAILED (%s): %s\n' "$BENCH_NAME" "$reason" >&2
    printf 'full results written to %s\n' "$report" >&2
}

# run_case <words|lines> <n-lines> <-w|-l> — create (or reuse) the text file,
# then race the selected wc against fastwc. Fails the benchmark the moment
# fastwc is slower or reports a different count.
run_case() {
    local mode="$1" lines="$2" flag="$3"
    local noun='lines'; [[ "$lines" -eq 1 ]] && noun='line'
    local label="${mode} (${lines} ${noun})"
    local file wc_count fast_count wc_ms fast_ms ratio verdict reason row
    local i d

    file=$(createtxt "$lines") || return 1

    # correctness: fastwc must report the same count as the reference wc
    wc_count=$(capture_count "${WC_CMD[@]}" "$flag" "$file")
    fast_count=$(capture_count "$FASTWC" "$flag" "$file")

    # speed: interleaved timing so both commands see identical cache warmth;
    # keep the minimum of $BENCH_REPS runs each to reduce noise
    wc_ms=''
    fast_ms=''
    for ((i = 0; i < BENCH_REPS; i++)); do
        d=$(time_ms "${WC_CMD[@]}" "$flag" "$file")
        [[ -z "$wc_ms" || "$d" -lt "$wc_ms" ]] && wc_ms="$d"

        d=$(time_ms "$FASTWC" "$flag" "$file")
        [[ -z "$fast_ms" || "$d" -lt "$fast_ms" ]] && fast_ms="$d"
    done

    if [[ -n "$wc_ms" && "$wc_ms" -gt 0 ]]; then
        ratio=$(awk -v f="$fast_ms" -v w="$wc_ms" 'BEGIN { printf "%.2fx", f / w }')
    else
        ratio='-'
    fi

    verdict='PASS'
    reason=''
    if [[ "$fast_count" != "$wc_count" ]]; then
        verdict='FAIL'
        reason="output mismatch (fastwc: ${fast_count}, ${BENCH_NAME} wc: ${wc_count})"
    elif (( fast_ms > wc_ms )); then
        verdict='FAIL'
        reason="fastwc was slower (fastwc: ${fast_ms}ms vs ${BENCH_NAME} wc: ${wc_ms}ms)"
    fi

    row=$(printf '%-28s %10s %10s %8s %s\n' \
        "$label" "wc: ${wc_ms}ms" "fastwc: ${fast_ms}ms" "$ratio" "$verdict")
    RESULT_ROWS+="${row}"$'\n'
    printf '%s\n' "$row"

    if [[ "$verdict" == 'FAIL' ]]; then
        write_failed_report "$label" "$reason" "$wc_ms" "$fast_ms"
        return 1
    fi
    return 0
}

# run_benchmark_suite — run every word and line case for the wc selected by
# checkwc(). Returns non-zero the first time fastwc loses.
run_benchmark_suite() {
    local rc=0 size

    printf 'benchmarking %s wc vs fastwc (%s interleaved runs each, minimum kept)\n' \
        "$BENCH_NAME" "$BENCH_REPS"
    printf '%-28s %10s %10s %8s %s\n' 'test' 'wc' 'fastwc' 'ratio' 'status'

    printf '%s\n' '--- words ---'
    for size in 1 10 100 1000 10000 100000; do
        run_case words "$size" -w || { rc=1; break; }
    done

    if [[ $rc -eq 0 ]]; then
        printf '%s\n' '--- lines ---'
        for size in 10000 100000 1000000 10000000; do
            run_case lines "$size" -l || { rc=1; break; }
        done
    fi

    if [[ $rc -eq 0 ]]; then
        printf '\nall %s benchmarks passed — fastwc was never slower than %s wc\n' \
            "$BENCH_NAME" "$BENCH_NAME"
    fi
    return $rc
}