#!/usr/bin/env bash
# Universal file preview — used by fzf widgets and as a standalone command.
# Usage: preview <file> [line]

file="${1:?usage: preview <file> [line]}"
line="${2:-}"

if [[ ! -e "$file" ]]; then
    echo "not found: $file"
    exit 1
fi

# Directory preview
if [[ -d "$file" ]]; then
    if command -v eza &>/dev/null; then
        eza --tree --level=2 --icons --color=always "$file"
    else
        ls -1A "$file"
    fi
    exit 0
fi

# Standalone mode: full terminal, can page output
# fzf mode: constrained to preview pane dimensions
is_fzf() { [[ -n "${FZF_PREVIEW_COLUMNS:-}" ]]; }

preview_image() {
    local w h
    if is_fzf; then
        w="$FZF_PREVIEW_COLUMNS"
        h="$FZF_PREVIEW_LINES"
        chafa --size="${w}x${h}" "$file"
    else
        w="$(tput cols)"
        h="$(tput lines)"
        printf '\033[?1049h'
        chafa --size="${w}x${h}" "$file"
        read -rsn1
        printf '\033[?1049l'
    fi
}

preview_pdf() {
    if is_fzf; then
        pdftotext -l 3 "$file" -
    else
        pdftotext "$file" - | bat --paging=always --style=plain --language=txt
    fi
}

preview_markdown() {
    if is_fzf; then
        bat --color=always --style=numbers ${line:+--highlight-line="$line"} "$file"
    elif command -v glow &>/dev/null; then
        glow -p "$file"
    else
        bat --paging=always --color=always --style=numbers "$file"
    fi
}

preview_archive() {
    local lower_file
    lower_file="$(printf '%s' "$file" | tr '[:upper:]' '[:lower:]')"
    local output
    case "$lower_file" in
        *.tar|*.tar.gz|*.tgz|*.tar.bz2|*.tbz2|*.tar.xz|*.txz)
            output="$(tar -tf "$file" | head -80)" ;;
        *.zip|*.jar|*.war)
            output="$(unzip -l "$file" | head -80)" ;;
        *.gz)
            output="$(gzip -l "$file")" ;;
        *)
            output="$(file "$file")" ;;
    esac
    if is_fzf; then
        printf '%s\n' "$output"
    else
        printf '%s\n' "$output" | bat --paging=always --style=plain --language=txt
    fi
}

preview_text() {
    local bat_args=(--color=always --style=numbers)
    if [[ -n "$line" ]]; then
        bat_args+=(--highlight-line="$line")
        if is_fzf; then
            local start=$((line > 30 ? line - 30 : 1))
            bat_args+=(--line-range="$start:$((line + 30))")
        fi
    elif is_fzf; then
        bat_args+=(--line-range=:100)
    fi
    if ! is_fzf; then
        bat_args+=(--paging=always)
    fi
    bat "${bat_args[@]}" "$file" 2>/dev/null || head -100 "$file"
}

preview_binary() {
    local output
    output="$(file "$file"; echo ""; hexdump -C "$file" | head -40)"
    if is_fzf; then
        printf '%s\n' "$output"
    else
        printf '%s\n' "$output" | bat --paging=always --style=plain --language=txt
    fi
}

# Route by extension
ext="${file##*.}"
ext="$(printf '%s' "$ext" | tr '[:upper:]' '[:lower:]')"

case "$ext" in
    png|jpg|jpeg|gif|webp|bmp|svg|ico|tiff|tif|avif)
        if command -v chafa &>/dev/null; then
            preview_image
        else
            file "$file"
        fi
        ;;
    pdf)
        if command -v pdftotext &>/dev/null; then
            preview_pdf
        else
            file "$file"
        fi
        ;;
    md|markdown|mdx)
        preview_markdown
        ;;
    tar|gz|tgz|bz2|tbz2|xz|txz|zip|jar|war)
        preview_archive
        ;;
    *)
        # MIME fallback for extensionless or ambiguous files
        mime="$(file --mime-type -b "$file" 2>/dev/null || echo "unknown")"
        case "$mime" in
            image/*)
                if command -v chafa &>/dev/null; then
                    preview_image
                else
                    file "$file"
                fi
                ;;
            application/pdf)
                if command -v pdftotext &>/dev/null; then
                    preview_pdf
                else
                    file "$file"
                fi
                ;;
            text/*|application/json|application/xml|application/javascript|*/x-shellscript)
                preview_text
                ;;
            *)
                preview_binary
                ;;
        esac
        ;;
esac