#!/bin/bash

# Structured progress emit for migrate flows. Phase 1's WebUI streams these
# JSON-per-line records and renders them. When MIGRATE_JSON_PROGRESS=1 the
# helper writes machine-readable JSON to fd 3 (or stdout if fd 3 isn't open);
# otherwise it's a no-op so the human CLI output stays clean.
#
# Usage:
#   migrateEmit phase=preflight status=running
#   migrateEmit phase=restore  status=running pct=50
#   migrateEmit phase=done     status=complete duration_seconds=42
#
# Keys with spaces or special chars should be passed pre-quoted (a=foo\ bar)
# or via the explicit setter form (rare — most callers use the simple kv form).
migrateEmit()
{
    [[ "$MIGRATE_JSON_PROGRESS" != "1" ]] && return 0

    local pair
    local first=1
    local out='{'
    for pair in "$@"; do
        local k="${pair%%=*}"
        local v="${pair#*=}"
        # Numeric values stay bare; everything else gets quoted + escaped.
        local rendered
        if [[ "$v" =~ ^-?[0-9]+(\.[0-9]+)?$ ]]; then
            rendered="$v"
        else
            local escaped="${v//\\/\\\\}"
            escaped="${escaped//\"/\\\"}"
            escaped="${escaped//$'\n'/\\n}"
            escaped="${escaped//$'\t'/\\t}"
            rendered="\"$escaped\""
        fi
        if (( first )); then
            out+="\"$k\":$rendered"
            first=0
        else
            out+=",\"$k\":$rendered"
        fi
    done
    out+='}'

    # fd 3 is the structured channel — Phase 1 opens it. If it's not open
    # (interactive CLI), fall back to stdout so dev/debug runs still see it.
    if { true >&3; } 2>/dev/null; then
        printf '%s\n' "$out" >&3
    else
        printf '%s\n' "$out"
    fi
}