#!/bin/bash
#
# agent-md - Manage AGENTS.md and CLAUDE.md files for AI coding agents
#

set -e

# Source utilities
SOURCE_DIR=$(chezmoi source-path 2>/dev/null || echo "$HOME/.local/share/chezmoi")
if [[ -f "$SOURCE_DIR/scripts/utils" ]]; then
    # shellcheck source=/dev/null
    . "$SOURCE_DIR/scripts/utils"
else
    # Minimal fallback if utils not available
    print_error() { echo "❌ $1"; }
    print_success() { echo "✅ $1"; }
    print_warning() { echo "⚠️  $1"; }
    print_info() { echo "ℹ️  $1"; }
    ask_for_confirmation() {
        read -r -p "$1 (y/n) " -n 1
        printf "\n"
        [[ $REPLY =~ ^[Yy]$ ]] && REPLY="y" || REPLY="n"
    }
    answer_is_yes() { [[ $REPLY =~ ^[Yy]$ ]]; }
    cmd_exists() { command -v "$1" &>/dev/null; }
    show_header() { echo "$1"; }
    show_section() { echo "── $1 ──"; }
fi

# Constants
readonly AGENTS_FILE="AGENTS.md"
readonly CLAUDE_DIR=".claude"
readonly CLAUDE_FILE="$CLAUDE_DIR/CLAUDE.md"
readonly SYMLINK_TARGET="../$AGENTS_FILE"

# Default template
read -r -d '' DEFAULT_TEMPLATE << 'EOF' || true
# AGENTS.md

## Project Overview
<!-- Brief description of the project -->

## Dev Environment
<!-- How to set up and run the project -->

## Testing
<!-- How to run tests -->

## Code Style
<!-- Coding conventions and style guidelines -->

## PR Guidelines
<!-- How to submit changes -->
EOF

# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

print_help() {
    cat <<HELPEOF
Usage: agent-md [OPTIONS]

Manage AGENTS.md and CLAUDE.md files for AI coding agents.

Options:
    --help, -h          Show this help message
    --check, -c         Only check status, don't modify files
    --force, -f         Skip confirmations
    --recursive, -r     Also process all git submodules

Description:
    Ensures AGENTS.md exists in project root as source of truth,
    with .claude/CLAUDE.md as a symlink for Claude Code compatibility.
HELPEOF
}

get_project_root() {
    if git rev-parse --show-toplevel 2>/dev/null; then
        return 0
    else
        pwd
        return 1
    fi
}

check_files() {
    local project_root="$1"

    AGENTS_EXISTS=false
    CLAUDE_EXISTS=false
    CLAUDE_ROOT_EXISTS=false
    CLAUDE_IS_SYMLINK=false
    CLAUDE_SYMLINK_CORRECT=false

    [[ -f "$project_root/$AGENTS_FILE" ]] && AGENTS_EXISTS=true

    if [[ -e "$project_root/$CLAUDE_FILE" ]] || [[ -L "$project_root/$CLAUDE_FILE" ]]; then
        CLAUDE_EXISTS=true
        if [[ -L "$project_root/$CLAUDE_FILE" ]]; then
            CLAUDE_IS_SYMLINK=true
            local target
            target=$(readlink "$project_root/$CLAUDE_FILE")
            [[ "$target" == "$SYMLINK_TARGET" ]] && CLAUDE_SYMLINK_CORRECT=true
        fi
    fi

    [[ -f "$project_root/CLAUDE.md" ]] && CLAUDE_ROOT_EXISTS=true

    return 0
}

create_with_pi() {
    local project_root="$1"

    if cmd_exists "pi"; then
        print_info "Launching pi agent..."
        local prompt="Create an AGENTS.md file for this project. Analyze the codebase structure, build tools, and existing documentation to generate appropriate sections for: Project Overview, Dev Environment setup, Testing instructions, Code Style guidelines, and PR Guidelines. Make it concise and practical for AI coding agents."
        (cd "$project_root" && pi "$prompt")

        if [[ -f "$project_root/$AGENTS_FILE" ]]; then
            print_success "Created $AGENTS_FILE"
            return 0
        else
            print_warning "pi did not create $AGENTS_FILE"
            return 1
        fi
    else
        return 1
    fi
}

create_with_claude_code() {
    local project_root="$1"

    if cmd_exists "claude"; then
        print_info "Launching claude-code with /init..."
        (cd "$project_root" && claude "/init")
        return 0
    else
        return 1
    fi
}

create_default_template() {
    local project_root="$1"
    echo "$DEFAULT_TEMPLATE" > "$project_root/$AGENTS_FILE"
    print_success "Created $AGENTS_FILE (default template)"
}

create_claude_symlink() {
    local project_root="$1"

    [[ ! -d "$project_root/$CLAUDE_DIR" ]] && mkdir -p "$project_root/$CLAUDE_DIR"

    if [[ -e "$project_root/$CLAUDE_FILE" ]] || [[ -L "$project_root/$CLAUDE_FILE" ]]; then
        rm "$project_root/$CLAUDE_FILE"
    fi

    (cd "$project_root/$CLAUDE_DIR" && ln -s "$SYMLINK_TARGET" "CLAUDE.md")
    print_success "Created $CLAUDE_FILE symlink"
}

handle_no_files() {
    local project_root="$1"
    local force="$2"

    print_warning "No AGENTS.md found"

    if [[ "$force" != "true" ]]; then
        ask_for_confirmation "Create AGENTS.md?"
        answer_is_yes || return 0
    fi

    local has_pi=false
    local has_claude=false
    cmd_exists "pi" && has_pi=true
    cmd_exists "claude" && has_claude=true

    if [[ "$has_pi" == "true" ]] || [[ "$has_claude" == "true" ]]; then
        local options=()
        [[ "$has_pi" == "true" ]] && options+=("pi agent")
        [[ "$has_claude" == "true" ]] && options+=("claude-code")
        options+=("Default template")

        local choice
        if cmd_exists "gum"; then
            choice=$(gum choose "${options[@]}")
        else
            echo "Choose creation method:"
            local i=1
            for opt in "${options[@]}"; do
                echo "$i) $opt"
                ((i++))
            done
            read -r -p "Choose [1-${#options[@]}]: " choice_num
            choice="${options[$((choice_num - 1))]}"
        fi

        case "$choice" in
            "pi agent")
                create_with_pi "$project_root" || create_default_template "$project_root"
                create_claude_symlink "$project_root"
                ;;
            "claude-code")
                create_with_claude_code "$project_root"
                # Exit after claude-code finishes - let user run agent-md again if needed
                exit 0
                ;;
            "Default template")
                create_default_template "$project_root"
                create_claude_symlink "$project_root"
                ;;
            *)
                create_default_template "$project_root"
                create_claude_symlink "$project_root"
                ;;
        esac
    else
        create_default_template "$project_root"
        create_claude_symlink "$project_root"
    fi
}

handle_only_agents() {
    local project_root="$1"

    if [[ "$CLAUDE_EXISTS" == "true" ]] && [[ "$CLAUDE_SYMLINK_CORRECT" == "true" ]]; then
        print_success "Already configured"
        return 0
    fi

    create_claude_symlink "$project_root"
}

handle_only_claude() {
    local project_root="$1"
    local force="$2"
    local source_file=""

    if [[ "$CLAUDE_ROOT_EXISTS" == "true" ]]; then
        source_file="$project_root/CLAUDE.md"
    elif [[ "$CLAUDE_EXISTS" == "true" ]] && [[ "$CLAUDE_IS_SYMLINK" == "false" ]]; then
        source_file="$project_root/$CLAUDE_FILE"
    fi

    print_info "Found CLAUDE.md, converting to AGENTS.md"

    if [[ "$force" != "true" ]]; then
        ask_for_confirmation "Move to AGENTS.md and create symlink?"
        answer_is_yes || return 0
    fi

    if [[ -n "$source_file" ]] && [[ -f "$source_file" ]]; then
        mv "$source_file" "$project_root/$AGENTS_FILE"
        print_success "Moved to $AGENTS_FILE"
    fi

    [[ "$CLAUDE_ROOT_EXISTS" == "true" ]] && [[ -f "$project_root/CLAUDE.md" ]] && rm "$project_root/CLAUDE.md"

    create_claude_symlink "$project_root"
}

handle_both_exist() {
    local project_root="$1"
    local force="$2"

    if [[ "$CLAUDE_SYMLINK_CORRECT" == "true" ]]; then
        print_success "Already configured"
        return 0
    fi

    print_warning "Both AGENTS.md and CLAUDE.md exist"

    local choice
    if cmd_exists "gum"; then
        choice=$(gum choose \
            "Keep AGENTS.md, replace CLAUDE.md with symlink" \
            "Show diff" \
            "Abort")
    else
        echo "1) Keep AGENTS.md, replace CLAUDE.md with symlink"
        echo "2) Show diff"
        echo "3) Abort"
        read -r -p "Choose [1-3]: " choice
        case "$choice" in
            1) choice="Keep AGENTS.md, replace CLAUDE.md with symlink" ;;
            2) choice="Show diff" ;;
            *) choice="Abort" ;;
        esac
    fi

    case "$choice" in
        "Keep AGENTS.md, replace CLAUDE.md with symlink")
            create_claude_symlink "$project_root"
            [[ "$CLAUDE_ROOT_EXISTS" == "true" ]] && rm "$project_root/CLAUDE.md"
            ;;
        "Show diff")
            local claude_path="$project_root/$CLAUDE_FILE"
            [[ "$CLAUDE_ROOT_EXISTS" == "true" ]] && claude_path="$project_root/CLAUDE.md"

            if cmd_exists "delta"; then
                delta "$project_root/$AGENTS_FILE" "$claude_path"
            else
                diff --color=auto -u "$project_root/$AGENTS_FILE" "$claude_path" || true
            fi
            handle_both_exist "$project_root" "$force"
            ;;
        *) ;;
    esac
}

show_status() {
    local project_root="$1"

    if [[ "$AGENTS_EXISTS" == "true" ]]; then
        print_success "$AGENTS_FILE exists"
    else
        print_warning "$AGENTS_FILE not found"
    fi

    if [[ "$CLAUDE_EXISTS" == "true" ]]; then
        if [[ "$CLAUDE_SYMLINK_CORRECT" == "true" ]]; then
            print_success "$CLAUDE_FILE symlink OK"
        elif [[ "$CLAUDE_IS_SYMLINK" == "true" ]]; then
            print_warning "$CLAUDE_FILE symlink incorrect"
        else
            print_warning "$CLAUDE_FILE is not a symlink"
        fi
    fi

    [[ "$CLAUDE_ROOT_EXISTS" == "true" ]] && print_warning "CLAUDE.md in root (wrong location)"
}

get_submodules() {
    local project_root="$1"
    # shellcheck disable=SC2016
    [[ -f "$project_root/.gitmodules" ]] && git -C "$project_root" submodule foreach --quiet 'echo $toplevel/$sm_path' 2>/dev/null
}

process_directory() {
    local project_root="$1"
    local check_only="$2"
    local force="$3"
    local label="${4:-}"

    [[ -n "$label" ]] && echo "[$label]"

    check_files "$project_root"

    if [[ "$check_only" == "true" ]]; then
        show_status "$project_root"
        return 0
    fi

    # Handle broken state: symlink exists but points to non-existent AGENTS.md
    if [[ "$AGENTS_EXISTS" == "false" ]] && [[ "$CLAUDE_IS_SYMLINK" == "true" ]]; then
        handle_no_files "$project_root" "$force"
    elif [[ "$AGENTS_EXISTS" == "false" ]] && [[ "$CLAUDE_EXISTS" == "false" ]] && [[ "$CLAUDE_ROOT_EXISTS" == "false" ]]; then
        handle_no_files "$project_root" "$force"
    elif [[ "$AGENTS_EXISTS" == "true" ]] && [[ "$CLAUDE_EXISTS" == "false" ]] && [[ "$CLAUDE_ROOT_EXISTS" == "false" ]]; then
        handle_only_agents "$project_root"
    elif [[ "$AGENTS_EXISTS" == "false" ]]; then
        handle_only_claude "$project_root" "$force"
    else
        handle_both_exist "$project_root" "$force"
    fi
}

main() {
    local check_only=false
    local force=false
    local recursive=false

    while [[ $# -gt 0 ]]; do
        case "$1" in
            --help|-h) print_help; exit 0 ;;
            --check|-c) check_only=true; shift ;;
            --force|-f) force=true; shift ;;
            --recursive|-r) recursive=true; shift ;;
            *) print_error "Unknown option: $1"; exit 1 ;;
        esac
    done

    local project_root
    local in_git=true
    project_root=$(get_project_root) || in_git=false

    [[ "$in_git" == "false" ]] && print_warning "Not in a git repository"

    process_directory "$project_root" "$check_only" "$force" "$project_root"

    if [[ "$recursive" == "true" ]] && [[ "$in_git" == "true" ]]; then
        local submodules
        submodules=$(get_submodules "$project_root")

        if [[ -n "$submodules" ]]; then
            while IFS= read -r submodule_path; do
                [[ -n "$submodule_path" ]] && [[ -d "$submodule_path" ]] && \
                    process_directory "$submodule_path" "$check_only" "$force" "$submodule_path"
            done <<< "$submodules"
        fi
    fi
}

main "$@"