#!/usr/bin/env bash
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
KIT_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"

MERGE_COPILOT_INSTRUCTIONS=0
DRY_RUN=0
PROJECT_ROOT=""

usage() {
    cat <<'EOF'
Usage: bootstrap/install.sh [PROJECT_ROOT] [--merge-copilot-instructions] [--dry-run]

Options:
  --merge-copilot-instructions   Opt-in: safely merge .github/copilot-instructions.md
  --dry-run                      Print planned changes without modifying files
  -h, --help                     Show this help message
EOF
}

log_action() {
    local message="$1"
    if [[ "$DRY_RUN" -eq 1 ]]; then
        echo "[dry-run] $message"
    else
        echo "$message"
    fi
}

run_or_dry() {
    if [[ "$DRY_RUN" -eq 1 ]]; then
        log_action "$*"
        return 0
    fi
    "$@"
}

while [[ $# -gt 0 ]]; do
    case "$1" in
        --merge-copilot-instructions)
            MERGE_COPILOT_INSTRUCTIONS=1
            shift
            ;;
        --dry-run)
            DRY_RUN=1
            shift
            ;;
        -h|--help)
            usage
            exit 0
            ;;
        -*)
            echo "Unknown option: $1" >&2
            usage >&2
            exit 1
            ;;
        *)
            if [[ -z "$PROJECT_ROOT" ]]; then
                PROJECT_ROOT="$1"
                shift
            else
                echo "Unexpected extra argument: $1" >&2
                usage >&2
                exit 1
            fi
            ;;
    esac
done

PROJECT_ROOT="${PROJECT_ROOT:-$(pwd)}"

MANAGED_BEGIN='<!-- BEGIN: myagent-kit (managed - do not edit) -->'
MANAGED_END='<!-- END: myagent-kit -->'
PROJECT_BEGIN='<!-- BEGIN: project-specific (safe to edit) -->'
PROJECT_END='<!-- END: project-specific -->'

count_occurrence() {
    local needle="$1"
    local file="$2"
    grep -cF "$needle" "$file" || true
}

build_managed_block() {
    local kit_file="$1"
    {
        printf '%s\n' "$MANAGED_BEGIN"
        cat "$kit_file"
        printf '\n%s\n' "$MANAGED_END"
    }
}

append_project_section_if_missing() {
    local file="$1"
    local project_begin_count
    local project_end_count

    project_begin_count="$(count_occurrence "$PROJECT_BEGIN" "$file")"
    project_end_count="$(count_occurrence "$PROJECT_END" "$file")"

    if [[ "$project_begin_count" -eq 0 && "$project_end_count" -eq 0 ]]; then
        cat >> "$file" <<EOF

$PROJECT_BEGIN
<!-- Add host-project-specific Copilot rules here. -->
$PROJECT_END
EOF
    elif [[ "$project_begin_count" -ne "$project_end_count" ]]; then
        return 1
    fi
}

validate_merged_copilot_file() {
    local file="$1"
    local managed_begin_count
    local managed_end_count
    local project_begin_count
    local project_end_count

    managed_begin_count="$(count_occurrence "$MANAGED_BEGIN" "$file")"
    managed_end_count="$(count_occurrence "$MANAGED_END" "$file")"
    project_begin_count="$(count_occurrence "$PROJECT_BEGIN" "$file")"
    project_end_count="$(count_occurrence "$PROJECT_END" "$file")"

    [[ "$managed_begin_count" -eq 1 ]] || return 1
    [[ "$managed_end_count" -eq 1 ]] || return 1
    [[ "$project_begin_count" -eq 1 ]] || return 1
    [[ "$project_end_count" -eq 1 ]] || return 1
}

merge_copilot_instructions() {
    local kit_file="$KIT_ROOT/base/.github/copilot-instructions.md"
    local host_file="$PROJECT_ROOT/.github/copilot-instructions.md"
    local backup_file="$host_file.bak"
    local tmp_file
    local managed_block
    local managed_begin_count
    local managed_end_count

    if [[ "$MERGE_COPILOT_INSTRUCTIONS" -ne 1 ]]; then
        return 0
    fi

    if [[ ! -f "$kit_file" ]]; then
        log_action "Skipped Copilot merge: kit template not found at $kit_file"
        return 0
    fi

    if [[ "$DRY_RUN" -eq 1 ]]; then
        if [[ ! -f "$host_file" ]]; then
            log_action "Would create and initialize $host_file with managed + project-specific sections"
            return 0
        fi

        managed_begin_count="$(count_occurrence "$MANAGED_BEGIN" "$host_file")"
        managed_end_count="$(count_occurrence "$MANAGED_END" "$host_file")"

        log_action "Would back up $host_file to $host_file.bak"
        if [[ "$managed_begin_count" -eq 1 && "$managed_end_count" -eq 1 ]]; then
            log_action "Would update managed myagent-kit section in $host_file"
        elif [[ "$managed_begin_count" -eq 0 && "$managed_end_count" -eq 0 ]]; then
            log_action "Would append managed myagent-kit section to $host_file"
        else
            log_action "Would fail: malformed managed marker pair in $host_file"
            return 1
        fi

        local project_begin_count
        local project_end_count
        project_begin_count="$(count_occurrence "$PROJECT_BEGIN" "$host_file")"
        project_end_count="$(count_occurrence "$PROJECT_END" "$host_file")"
        if [[ "$project_begin_count" -eq 0 && "$project_end_count" -eq 0 ]]; then
            log_action "Would append project-specific editable section to $host_file"
        elif [[ "$project_begin_count" -ne "$project_end_count" ]]; then
            log_action "Would fail: malformed project-specific marker pair in $host_file"
            return 1
        fi
        return 0
    fi

    managed_block="$(build_managed_block "$kit_file")"
    tmp_file="$(mktemp)"

    if [[ ! -f "$host_file" ]]; then
        {
            printf '%s\n' "$managed_block"
            printf '\n%s\n' "$PROJECT_BEGIN"
            printf '<!-- Add host-project-specific Copilot rules here. -->\n'
            printf '%s\n' "$PROJECT_END"
        } > "$host_file"
        validate_merged_copilot_file "$host_file"
        log_action "Created and initialized $host_file"
        rm -f "$tmp_file"
        return 0
    fi

    cp "$host_file" "$backup_file"
    managed_begin_count="$(count_occurrence "$MANAGED_BEGIN" "$host_file")"
    managed_end_count="$(count_occurrence "$MANAGED_END" "$host_file")"

    if [[ "$managed_begin_count" -eq 1 && "$managed_end_count" -eq 1 ]]; then
        awk \
            -v begin="$MANAGED_BEGIN" \
            -v end="$MANAGED_END" \
            -v block="$managed_block" '
                BEGIN {
                    in_block = 0
                    replaced = 0
                }
                $0 == begin {
                    if (!replaced) {
                        print block
                        replaced = 1
                    }
                    in_block = 1
                    next
                }
                $0 == end {
                    in_block = 0
                    next
                }
                !in_block {
                    print
                }
                END {
                    if (!replaced) {
                        print ""
                        print block
                    }
                }
            ' "$host_file" > "$tmp_file"
    elif [[ "$managed_begin_count" -eq 0 && "$managed_end_count" -eq 0 ]]; then
        {
            cat "$host_file"
            printf '\n%s\n' "$managed_block"
        } > "$tmp_file"
    else
        echo "Malformed managed marker pair in $host_file" >&2
        cp "$backup_file" "$host_file"
        rm -f "$tmp_file"
        return 1
    fi

    mv "$tmp_file" "$host_file"
    append_project_section_if_missing "$host_file"
    validate_merged_copilot_file "$host_file"
    log_action "Merged $host_file (backup: $backup_file)"
}

run_or_dry mkdir -p "$PROJECT_ROOT/.github/prompts" \
                  "$PROJECT_ROOT/.github/instructions" \
                  "$PROJECT_ROOT/.github/ISSUE_TEMPLATE"

run_or_dry cp "$KIT_ROOT/base/.github/prompts/"*.prompt.md "$PROJECT_ROOT/.github/prompts/"
run_or_dry cp "$KIT_ROOT/base/.github/instructions/"*.instructions.md "$PROJECT_ROOT/.github/instructions/"
run_or_dry cp "$KIT_ROOT/base/.github/ISSUE_TEMPLATE/"*.md "$PROJECT_ROOT/.github/ISSUE_TEMPLATE/"
if [[ -f "$KIT_ROOT/base/.github/pull_request_template.md" ]]; then
    run_or_dry cp "$KIT_ROOT/base/.github/pull_request_template.md" "$PROJECT_ROOT/.github/pull_request_template.md"
fi

merge_copilot_instructions

log_action "Installed myagent-kit assets into $PROJECT_ROOT/.github"