#!/bin/bash

BIB_FILE="$HOME/latex/uni.bib"
CORRECTION_METHOD="sed -n -E 's/.*((DOI|doi)((\.(org))?\/?|:? *))([^: ]+[^ .]).*/doi:\6/p; T; q'"

function get_doi_from_pdf {
    local pdf="$1"
    local doi
    doi=$(pdfinfo "$pdf" 2>/dev/null | eval "$CORRECTION_METHOD")
    if [ -z "$doi" ]; then
        doi=$(pdftotext -q -l 1 "$pdf" - 2>/dev/null | eval "$CORRECTION_METHOD")
    fi
    echo "$doi"
}

function normalize_doi {
    local doi="$1"
    echo "${doi,,}"
}

function process_doi {
    local doi="$1"
    local bibtex_entry
    bibtex_entry=$(curl -s "https://api.crossref.org/works/$doi/transform/application/x-bibtex" -w "\\n" | sed '/^@[a-z]\+{[^[:space:]]\+[0-9]\{4\},/{
    s/\([A-Z]\)/\L\1/g
    s/_//g
    s/[0-9]*\([0-9]\{2\}\)/\1/g
}')
    red_color='\033[0;31m'
    reset_color='\033[0m'

    echo -e "${red_color}$bibtex_entry${reset_color}"

    if [[ -z "$bibtex_entry" || ! "$bibtex_entry" =~ ^@ ]]; then
        echo "Failed to fetch bibtex entry for DOI: $doi"
        return 1
    fi

    local normalized_doi="${doi#doi:}"
    if ! grep -q -E "doi\s*=\s*\{${normalized_doi//(/\\(}\}" "$BIB_FILE"; then
        if [ -s "$BIB_FILE" ]; then
            echo "" >> "$BIB_FILE"
        fi
        echo "$bibtex_entry" >> "$BIB_FILE"
        echo "Added bibtex entry for DOI: $doi"
    else
        echo "Bibtex entry for DOI: $doi already exists in the file."
    fi
}

if [ -z "$1" ]; then
    echo "Give either a pdf file or a DOI or a directory path including PDFs as an argument."
    exit 1
fi

if [ -d "$1" ]; then
    for pdf in "$1"/*.pdf; do
        doi=$(get_doi_from_pdf "$pdf")
        if [ -n "$doi" ]; then
            doi=$(normalize_doi "$doi")
            process_doi "$doi"
        else
            echo "Could not find DOI in PDF file: $pdf"
        fi
    done
elif [ -f "$1" ] && [[ "$1" =~ \.pdf$ ]]; then
    doi=$(get_doi_from_pdf "$1")
    if [ -n "$doi" ]; then
        doi=$(normalize_doi "$doi")
        process_doi "$doi"
    else
        echo "Could not find DOI in PDF file: $1"
    fi
else
    doi=$(echo "$1" | eval "$CORRECTION_METHOD")
    if [ -n "$doi" ]; then
        doi=$(normalize_doi "$doi")
        process_doi "$doi"
    else
        echo "Invalid DOI provided: $1"
    fi
fi