#!/bin/bash
# download_helper.sh - Универсальный загрузчик с fallback для РФ
# Поддерживает: HTTPS_PROXY, зеркала GitHub, локальные кэши, raw.githubusercontent.com

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && cd .. && pwd)"
CACHE_DIR="$SCRIPT_DIR/.cache"
mkdir -p "$CACHE_DIR"

# Read proxy from environment or .env file
load_proxy() {
    if [[ -f "$SCRIPT_DIR/.env" ]]; then
        source "$SCRIPT_DIR/.env"
    fi
    # Priority: runtime env > .env > system env
    if [[ -n "${GITHUB_PROXY:-}" ]]; then
        HTTPS_PROXY="$GITHUB_PROXY"
    fi
    if [[ -n "${HTTPS_PROXY:-}" ]]; then
        export HTTPS_PROXY="$HTTPS_PROXY"
    fi
    if [[ -n "${HTTP_PROXY:-}" ]]; then
        export HTTP_PROXY="$HTTP_PROXY"
    fi
}

# Detect available download tool
detect_curl() {
    local cmd="curl -sfL --max-time 15 --retry 2"
    if [[ -n "${HTTPS_PROXY:-}" ]]; then
        cmd="curl -sfL --max-time 15 --retry 2 --proxy '$HTTPS_PROXY'"
    fi
    echo "$cmd"
}

# Try downloading multiple sources, use cache, log failures
download_with_fallback() {
    local output="$1"
    shift
    local sources=("$@")
    local curl_cmd
    curl_cmd=$(detect_curl)

    load_proxy

    # Try local cache first
    local cache_file="$CACHE_DIR/$(echo "$output" | tr '/\\' '_')"
    if [[ -f "$cache_file" ]] && [[ -s "$cache_file" ]]; then
        echo "[OK] Using cached: $(basename "$cache_file")"
        cp "$cache_file" "$output"
        return 0
    fi

    # Try each source
    local success=0
    for src in "${sources[@]}"; do
        echo "[*] Trying: $src"
        if $curl_cmd "$src" -o "$output.tmp" 2>/dev/null; then
            if [[ -s "$output.tmp" ]]; then
                mv "$output.tmp" "$output"
                cp "$output" "$cache_file"
                echo "[OK] Downloaded from: $src"
                success=1
                break
            fi
        fi
        rm -f "$output.tmp"
    done

    if [[ "$success" -eq 0 ]]; then
        echo "[FAIL] All download sources exhausted."
        return 1
    fi
}

# Download GitHub repository as tarball (faster than clone for read-only)
clone_repo_fallback() {
    local repo="$1"          # e.g., Flowseal/zapret-discord-youtube
    local branch="${2:-main}"
    local output_dir="$3"

    local curl_cmd
    curl_cmd=$(detect_curl)

    # Try git clone with proxy
    local git_env=""
    if [[ -n "${HTTPS_PROXY:-}" ]]; then
        git_env="GIT_SSL_NO_VERIFY=1"
    fi

    # Try direct git clone
    if GIT_SSL_NO_VERIFY=1 git clone --depth=1 --single-branch --branch "$branch" "https://github.com/$repo.git" "$output_dir" 2>/dev/null; then
        echo "[OK] git clone success"
        return 0
    fi

    # Try tarball download (often works when git blocked)
    local tarball="/tmp/repo-$$.tar.gz"
    echo "[*] Trying tarball download..."
    if $curl_cmd "https://api.github.com/repos/$repo/tarball/$branch" -o "$tarball" 2>/dev/null; then
        if [[ -s "$tarball" ]]; then
            mkdir -p "$output_dir"
            tar -xzf "$tarball" -C "$output_dir" --strip-components=1
            rm -f "$tarball"
            echo "[OK] Downloaded tarball"
            return 0
        fi
    fi
    rm -f "$tarball"

    # Try ZIP download
    local zipfile="/tmp/repo-$$.zip"
    echo "[*] Trying ZIP download..."
    if $curl_cmd "https://api.github.com/repos/$repo/zipball/$branch" -o "$zipfile" 2>/dev/null; then
        if [[ -s "$zipfile" ]]; then
            mkdir -p "$output_dir"
            unzip -q "$zipfile" -d "/tmp/repo-$$-extract"
            mv "/tmp/repo-$$-extract"/*/ "$output_dir" 2>/dev/null || true
            rm -rf "$zipfile" "/tmp/repo-$$-extract"
            echo "[OK] Downloaded ZIP"
            return 0
        fi
    fi
    rm -f "$zipfile"

    # Try mirror: gitea / gitlab / codeberg
    local mirrors=(
        "https://ghproxy.com/https://github.com/$repo.git"
        "https://hub.fastgit.xyz/$repo.git"
    )
    for mirror in "${mirrors[@]}"; do
        echo "[*] Trying mirror: $mirror"
        if GIT_SSL_NO_VERIFY=1 git clone --depth=1 --single-branch --branch "$branch" "$mirror" "$output_dir" 2>/dev/null; then
            echo "[OK] Clone from mirror"
            return 0
        fi
        rm -rf "$output_dir"
    done

    echo "[FAIL] Cannot clone repository. Check proxy or use prepare_offline_bundle.sh"
    return 1
}

# Generic file download from remote with mirrors
download_file_fallback() {
    local output="$1"
    local primary_url="$2"
    local mirrors=(
        "https://ghproxy.com/$primary_url"
        "https://raw.fastgit.xyz/${primary_url#https://raw.githubusercontent.com/}"
    )

    local all_sources=("$primary_url" "${mirrors[@]}")
    download_with_fallback "$output" "${all_sources[@]}"
}