#!/usr/bin/env bash

set -euo pipefail

# Script to manually update Cursor version/hashes used by the flake
# Usage:
#   ./update-cursor.sh                # auto: pick highest of ("latest" pointer, current major.minor pointer)
#   ./update-cursor.sh 2.2.44         # pin exact version
#   ./update-cursor.sh latest         # follow the "latest" pointer only
#   ./update-cursor.sh 2.2            # follow a major.minor pointer only

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
FLAKE_FILE="$SCRIPT_DIR/flake.nix"
MANAGED_BEGIN="# BEGIN managed by ./update-cursor.sh"
MANAGED_END="# END managed by ./update-cursor.sh"
INDENT="      "

CHANNEL_FOR_SYSTEM_x86_64_linux="linux-x64"
CHANNEL_FOR_SYSTEM_aarch64_linux="linux-arm64"

# Extract Cursor semver from a resolved download URL (Location header).
extract_version_from_url() {
    local url="${1:-}"
    echo "$url" | grep -Eo 'Cursor-[0-9]+\.[0-9]+\.[0-9]+' | sed 's/Cursor-//' || true
}

# Get a redirect URL for a given pointer (e.g. latest, 2.2, 2.2.44) and channel.
get_redirect_url() {
    local channel="${1:?channel is required}"
    local pointer="${2:?pointer is required}"
    local url="https://api2.cursor.sh/updates/download/golden/${channel}/cursor/${pointer}"

    # Avoid stale CDN/proxy cache results for fast-moving pointers like "latest".
    curl -sS -I \
        -H 'Cache-Control: no-cache' \
        -H 'Pragma: no-cache' \
        "$url" \
      | awk 'BEGIN{IGNORECASE=1} $1=="location:" {print $2; exit}' \
      | tr -d '\r\n'
}

# Resolve an exact version to a stable downloads.cursor.com URL.
#
# Guardrail: Cursor's API has been observed to sometimes redirect an "exact version" URL
# (e.g. /cursor/2.2.44) to an older AppImage (e.g. 2.2.43). When that happens, we retry via
# the major.minor pointer (e.g. /cursor/2.2) and only proceed if it resolves to the requested
# version.
resolve_download_url_for_version() {
    local channel="${1:?channel is required}"
    local version="${2:?version is required}"

    local redirect_url resolved_version
    redirect_url="$(get_redirect_url "$channel" "$version")"
    if [[ -z "$redirect_url" ]]; then
        echo "Error: Could not resolve Location header for ${channel} ${version}" >&2
        return 1
    fi

    resolved_version="$(extract_version_from_url "$redirect_url")"
    if [[ "$resolved_version" == "$version" ]]; then
        echo "$redirect_url"
        return 0
    fi

    local minor_pointer fallback_redirect fallback_resolved
    minor_pointer="$(get_track_from_version "$version")"
    echo "Warning: ${channel} ${version} resolved to ${resolved_version:-unknown}; retrying via pointer ${minor_pointer}" >&2
    fallback_redirect="$(get_redirect_url "$channel" "$minor_pointer")"
    if [[ -z "$fallback_redirect" ]]; then
        echo "Error: Could not resolve Location header for fallback ${channel} ${minor_pointer}" >&2
        return 1
    fi

    fallback_resolved="$(extract_version_from_url "$fallback_redirect")"
    if [[ "$fallback_resolved" != "$version" ]]; then
        echo "Error: Could not resolve requested version $version for channel $channel." >&2
        echo "Tried:" >&2
        echo "  - /cursor/${version} -> ${resolved_version:-unknown} ($redirect_url)" >&2
        echo "  - /cursor/${minor_pointer} -> ${fallback_resolved:-unknown} ($fallback_redirect)" >&2
        echo "Upstream pointers/caches are inconsistent; try again later." >&2
        return 1
    fi

    echo "$fallback_redirect"
}

# Resolve a pointer (e.g. latest, 2.2) into an actual semver (e.g. 2.2.44).
get_latest_version() {
    local track="${1:-latest}"

    local redirect_url
    # Version discovery can just use linux-x64; the resolved version is shared across architectures.
    redirect_url="$(get_redirect_url "$CHANNEL_FOR_SYSTEM_x86_64_linux" "$track")"

    if [[ -n "$redirect_url" ]]; then
        # Extract version from URL like: .../Cursor-2.2.44-x86_64.AppImage
        echo "$redirect_url" | grep -Eo 'Cursor-[0-9]+\.[0-9]+\.[0-9]+' | sed 's/Cursor-//'
    else
        echo "Error: Could not get redirect URL for track: $track" >&2
        return 1
    fi
}

# True if arg looks like a full semver (e.g. 2.2.44).
is_full_semver() {
    [[ "${1:-}" =~ ^[0-9]+\.[0-9]+\.[0-9]+$ ]]
}

# True if arg looks like a pointer we can resolve (e.g. latest, 2.2).
is_pointer() {
    [[ "${1:-}" == "latest" || "${1:-}" =~ ^[0-9]+\.[0-9]+$ ]]
}

is_ci() {
    [[ -n "${CI:-}" || -n "${GITHUB_ACTIONS:-}" || -n "${GITEA_ACTIONS:-}" ]]
}

write_version_output() {
    local value="$1"
    if [[ -n "${GITHUB_OUTPUT:-}" ]]; then
        echo "CURSOR_VERSION_INFO=$value" >> "$GITHUB_OUTPUT"
    fi
}

# Function to get current version from flake.nix managed block
get_current_version() {
    awk -v begin="$MANAGED_BEGIN" -v end="$MANAGED_END" '
      $0 ~ begin {inblock=1; next}
      $0 ~ end {inblock=0}
      inblock && match($0, /version = "([^"]+)";/, m) { print m[1]; exit }
    ' "$FLAKE_FILE"
}

# Derive major.minor track from a full version (e.g. 2.2.43 -> 2.2).
get_track_from_version() {
    local version="${1:?version is required}"
    echo "$version" | awk -F. '{print $1 "." $2}'
}

# Return the highest of the provided dotted versions using natural version sort.
semver_max() {
    # Accepts N args; prints the max.
    printf '%s\n' "$@" | grep -E '^[0-9]+\.[0-9]+\.[0-9]+$' | sort -V | tail -n1
}

# Function to compute sha256 for a given system+version
prefetch_sha256() {
    local system="$1"
    local url="$2"
    local channel=""

    case "$system" in
        x86_64-linux) channel="$CHANNEL_FOR_SYSTEM_x86_64_linux" ;;
        aarch64-linux) channel="$CHANNEL_FOR_SYSTEM_aarch64_linux" ;;
        *) echo "Error: Unsupported system: $system" >&2; return 1 ;;
    esac

    if ! command -v nix-prefetch-url >/dev/null 2>&1; then
        echo "Error: nix-prefetch-url not found. Please install Nix (or nix-prefetch-url) and retry." >&2
        return 1
    fi

    # IMPORTANT: this function is captured by command substitution. Keep stdout as the hash only.
    echo "Prefetching ($system) from resolved URL: $url" >&2

    local out hash
    out="$(nix-prefetch-url --type sha256 "$url" 2>&1)"
    echo "$out" >&2

    # Extract the Nix base32 sha256 hash (52 chars, Nix alphabet).
    hash="$(echo "$out" | grep -Eo '[0-9abcdfghijklmnpqrsvwxyz]{52}' | tail -n1 || true)"
    if [[ -z "$hash" ]]; then
        echo "Error: Could not parse sha256 from nix-prefetch-url output for $system" >&2
        return 1
    fi

    echo "$hash"
}

# Update flake.nix managed block with a new version + per-system urls/hashes
update_release() {
    local version="$1"

    echo "Computing hashes for version: $version"

    local url_x86 url_aarch64 sha_x86 sha_aarch64
    url_x86="$(resolve_download_url_for_version "$CHANNEL_FOR_SYSTEM_x86_64_linux" "$version")"
    url_aarch64="$(resolve_download_url_for_version "$CHANNEL_FOR_SYSTEM_aarch64_linux" "$version")"

    sha_x86="$(prefetch_sha256 x86_64-linux "$url_x86")"
    sha_aarch64="$(prefetch_sha256 aarch64-linux "$url_aarch64")"

    echo "x86_64-linux sha256: $sha_x86"
    echo "aarch64-linux sha256: $sha_aarch64"

    if ! grep -qF "$MANAGED_BEGIN" "$FLAKE_FILE" || ! grep -qF "$MANAGED_END" "$FLAKE_FILE"; then
        echo "Error: Could not find managed block markers in $FLAKE_FILE" >&2
        echo "Expected lines containing:" >&2
        echo "  $MANAGED_BEGIN" >&2
        echo "  $MANAGED_END" >&2
        return 1
    fi

    # Create backup
    cp "$FLAKE_FILE" "$FLAKE_FILE.backup"

    local tmp_file
    tmp_file="$(mktemp -t cursor-flake-update-XXXXXX)"

    local inblock=0
    while IFS= read -r line; do
        if [[ "$inblock" -eq 0 && "$line" == *"$MANAGED_BEGIN"* ]]; then
            printf '%s\n' "$line" >> "$tmp_file"

            cat >> "$tmp_file" <<EOF
${INDENT}version = "$version";
${INDENT}sources = {
${INDENT}  x86_64-linux = {
${INDENT}    url = "$url_x86";
${INDENT}    sha256 = "$sha_x86";
${INDENT}  };
${INDENT}  aarch64-linux = {
${INDENT}    url = "$url_aarch64";
${INDENT}    sha256 = "$sha_aarch64";
${INDENT}  };
${INDENT}};
EOF

            inblock=1
            continue
        fi

        if [[ "$inblock" -eq 1 && "$line" == *"$MANAGED_END"* ]]; then
            printf '%s\n' "$line" >> "$tmp_file"
            inblock=0
            continue
        fi

        if [[ "$inblock" -eq 1 ]]; then
            continue
        fi

        printf '%s\n' "$line" >> "$tmp_file"
    done < "$FLAKE_FILE"

    mv "$tmp_file" "$FLAKE_FILE"
    echo "Updated flake.nix managed block with version $version"
}

# Function to test the flake
test_flake() {
    echo "Testing flake..."
    if command -v nix >/dev/null 2>&1; then
        nix flake check --no-build
        echo "Flake check passed!"
    else
        echo "Warning: nix command not found. Skipping flake check."
    fi
}

# Main logic
main() {
    local target_version="${1:-}"
    
    echo "Cursor Flake Updater"
    echo "==================="
    
    # Get current version
    local current_version
    current_version=$(get_current_version)
    echo "Current version: $current_version"
    
    # Determine target version
    if [[ -n "$target_version" ]]; then
        if is_full_semver "$target_version"; then
            echo "Target version (pinned): $target_version"
        elif is_pointer "$target_version"; then
            echo "Target pointer: $target_version"
            target_version="$(get_latest_version "$target_version")"
            echo "Resolved version: $target_version"
        else
            echo "Error: Invalid argument: $target_version" >&2
            echo "Expected: full version (e.g. 2.2.44) or pointer (latest or 2.2)" >&2
            exit 1
        fi
    else
        # Auto mode:
        # - Check "latest" to allow moving to new major/minor (e.g. 2.3.x)
        # - Check current major.minor line to avoid missing patches when "latest" lags (e.g. 2.2.44 vs latest=2.2.43)
        # - Also check latest's own major.minor line (if latest=2.3.0 but 2.3 pointer is 2.3.1)
        local current_track v_latest latest_track v_latest_track v_current_track
        current_track="$(get_track_from_version "$current_version")"

        echo "Fetching pointers: latest, $current_track"
        v_latest="$(get_latest_version latest)"
        latest_track="$(get_track_from_version "$v_latest")"
        v_current_track="$(get_latest_version "$current_track")"

        if [[ "$latest_track" != "$current_track" ]]; then
            echo "Latest is on a different minor: $latest_track (also checking it)"
            v_latest_track="$(get_latest_version "$latest_track")"
        else
            v_latest_track="$v_latest"
        fi

        target_version="$(semver_max "$v_latest" "$v_current_track" "$v_latest_track")"
        echo "Resolved: latest=$v_latest pointer($current_track)=$v_current_track pointer($latest_track)=$v_latest_track -> chosen=$target_version"
    fi
    
    # Same semver but Cursor may republish the AppImage (hash/url drift). In CI, always re-prefetch.
    if [[ "$target_version" == "$current_version" ]]; then
        if is_ci; then
            echo "Version unchanged ($current_version); re-prefetching URLs and hashes for upstream drift..."
            update_release "$target_version"
            rm -f "$FLAKE_FILE.backup"
            if git diff --quiet -- "$FLAKE_FILE" 2>/dev/null; then
                echo "Hashes and URLs already match upstream."
                write_version_output "no_update"
                exit 0
            fi
            test_flake
            echo "Refreshed hashes for Cursor $target_version"
            write_version_output "completed:$current_version:$target_version"
            exit 0
        fi
        echo "No update needed. Current version is up to date."
        write_version_output "no_update"
        exit 0
    fi

    echo "Update needed: $current_version -> $target_version"

    if is_ci; then
        echo "Running in CI mode, auto-confirming update..."
        REPLY="y"
    else
        read -p "Do you want to proceed with the update? (y/N): " -n 1 -r
        echo
    fi

    if [[ $REPLY =~ ^[Yy]$ ]]; then
        update_release "$target_version"
        rm -f "$FLAKE_FILE.backup"
        test_flake
        echo "Update completed successfully!"
        write_version_output "completed:$current_version:$target_version"
        echo "You can now commit the changes:"
        echo "  git add flake.nix"
        echo "  git commit -m \"Update Cursor to version $target_version\""
    else
        echo "Update cancelled."
        exit 1
    fi
}

# Check dependencies
check_dependencies() {
    local missing_deps=()
    
    if ! command -v curl >/dev/null 2>&1; then
        missing_deps+=("curl")
    fi
    if [[ ! -f "$FLAKE_FILE" ]]; then
        missing_deps+=("flake.nix (missing file)")
    fi
    
    if [[ ${#missing_deps[@]} -gt 0 ]]; then
        echo "Error: Missing required dependencies: ${missing_deps[*]}"
        echo "Please install them and try again."
    exit 1
fi
}

# Run main function
check_dependencies
main "$@"