queries.rs

//! SQL queries for the database.
//!
//! Some of these are functions that return a query that is dynamically generated based on requirements.

use crate::qp::Exam;

/// Database initialization query. Not used by the backend directly.
#[allow(dead_code)]
const INIT_DB: &str = "
CREATE TABLE IF NOT EXISTS iqps (
	id integer primary key GENERATED ALWAYS AS identity,
	course_code TEXT NOT NULL DEFAULT '',
	course_name TEXT NOT NULL DEFAULT '',
	year INTEGER NOT NULL,
    exam TEXT NOT NULL DEFAULT '',
    semester TEXT NOT NULL DEFAULT '',
    note TEXT NOT NULL DEFAULT '',
    filelink TEXT NOT NULL,
    from_library BOOLEAN DEFAULT FALSE,
    upload_timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    approve_status BOOLEAN DEFAULT FALSE,
    approved_by TEXT DEFAULT '',
    is_deleted BOOLEAN DEFAULT FALSE,
    fts_course_details tsvector GENERATED ALWAYS AS (to_tsvector('english', course_code || ' ' || course_name)) stored
);
CREATE INDEX IF NOT EXISTS iqps_fts ON iqps USING gin (fts_course_details);
CREATE EXTENSION pg_trgm;
CREATE INDEX IF NOT EXISTS idx_course_name_trgm ON iqps USING gin (course_name gin_trgm_ops);";

/// Query to get similar papers. Matches `course_code` ($1) always. Other parameters are optional and can be enabled or disabled using the arguments to this function.
///
/// Query parameters:
/// `$1` - `course_code``
/// `$2` - `year`
/// `$3` - `semester`
/// `$3` - `exam`
pub fn get_similar_papers_query(year: bool, semester: bool, exam: bool) -> String {
    let mut param_num = 1;

    format!(
        "SELECT {} from iqps where is_deleted=false and course_code = $1 {} {} {}",
        ADMIN_DASHBOARD_QP_FIELDS,
        if year {
            param_num += 1;
            format!("AND year=${}", param_num)
        } else {
            "".to_string()
        },
        if semester {
            param_num += 1;
            format!("AND semester=${}", param_num)
        } else {
            "".to_string()
        },
        if exam {
            param_num += 1;
            format!("AND exam=${}", param_num)
        } else {
            "".to_string()
        },
    )
}

/// Soft deletes a paper (sets `approve_status` to false and `is_deleted` to true) of an uploaded paper.
pub const SOFT_DELETE_BY_ID: &str =
    "UPDATE iqps SET approve_status=false, is_deleted = true WHERE id=$1 AND from_library = false";

/// Get a paper ([`crate::db::models::DBAdminDashboardQP`]) with the given id (first parameter `$1`)
pub fn get_get_paper_by_id_query() -> String {
    format!(
        "SELECT {} FROM iqps WHERE id = $1",
        ADMIN_DASHBOARD_QP_FIELDS
    )
}

/// Returns a query that updates a paper's details by id ($1) (course_code, course_name, year, semester, exam, note, approve_status, filelink). `approved_by` optionally included if the edit is also used for approval.
///
/// The query also returns all the admin dashboard qp fields of the edited paper
///
/// Query parameters:
/// - $1: `id`
/// - $2: `course_code`
/// - $3: `course_name`
/// - $4: `year`
/// - $5: `semester`
/// - $6: `exam`
/// - $7: `note`
/// - $8: `approve_status`
/// - $9: `filelink`
/// - $10: `approved_by`
pub fn get_edit_paper_query(approval: bool) -> String {
    format!(
		"UPDATE iqps set course_code=$2, course_name=$3, year=$4, semester=$5, exam=$6, note=$7, approve_status=$8, filelink=$9{} WHERE id=$1 AND is_deleted=false RETURNING {}",
		if approval {", approved_by=$10"} else {""},
        ADMIN_DASHBOARD_QP_FIELDS
	)
}

/// Gets all unapproved papers ([`crate::db::models::DBAdminDashboardQP`]) from the database
pub fn get_all_unapproved_query() -> String {
    format!("SELECT {} FROM iqps WHERE approve_status = false and is_deleted=false ORDER BY upload_timestamp ASC", ADMIN_DASHBOARD_QP_FIELDS)
}

/// An enum representing the exam filter for the search query
pub enum ExamFilter {
    Exam(Exam), // Match an exact exam or use `ct` substring match
    Any,        // Match anything
    MidEnd,     // Midsem or endsem
}

impl TryFrom<&String> for ExamFilter {
    type Error = color_eyre::eyre::Error;

    fn try_from(value: &String) -> Result<Self, Self::Error> {
        if value.is_empty() {
            Ok(ExamFilter::Any)
        } else if value == "midend" {
            Ok(ExamFilter::MidEnd)
        } else {
            Ok(ExamFilter::Exam(Exam::try_from(value)?))
        }
    }
}

/// Returns the query for searching question papers. It is mostly voodoo, see [blog post](https://rajivharlalka.in/posts/iqps-search-development/).
///
/// Optionally, the `exam` argument can be used to also add a clause to match the exam field.
///
/// Query parameters:
/// $1 - Search query
/// $2 - Exam filter string (can be midsem, endsem, midend, or ct)
///
/// Returns the query and a boolean representing whether the second argument is required
pub fn get_qp_search_query(exam_filter: ExamFilter) -> (String, bool) {
    let (exam_filter, use_exam_arg) = match exam_filter {
        ExamFilter::Any => ("", false),
        ExamFilter::MidEnd => (
            "WHERE (exam = 'midsem' OR exam = 'endsem' OR exam = '')",
            false,
        ),
        ExamFilter::Exam(exam) => match exam {
            Exam::CT(_) => ("WHERE (exam LIKE 'ct%' OR exam = '')", false),
            _ => ("WHERE (exam = $2 OR exam = '')", true),
        },
    };

    (
        format!("
            WITH filtered AS (
                SELECT * from iqps {exam_filter} ORDER BY year DESC
            ),
            fuzzy AS (
                SELECT id,
                similarity(course_code || ' ' || course_name, $1) AS sim_score,
                row_number() OVER (ORDER BY similarity(course_code || ' ' || course_name, $1) DESC) AS rank_ix
                FROM filtered
                WHERE (course_code || ' ' || course_name) %>> $1 AND approve_status = true
                ORDER BY rank_ix
                LIMIT 30
            ),
            full_text AS (
                SELECT id,
                    ts_rank_cd(fts_course_details, websearch_to_tsquery($1)) AS rank_score,
                    row_number() OVER (ORDER BY ts_rank_cd(fts_course_details, websearch_to_tsquery($1)) DESC) AS rank_ix
                FROM filtered
                WHERE fts_course_details @@ websearch_to_tsquery($1) AND approve_status = true
                ORDER BY rank_ix
                LIMIT 30
            ),
            partial_search AS (
                SELECT id,
                    ts_rank_cd(fts_course_details, {to_tsquery}) AS rank_score,
                    row_number() OVER (ORDER BY ts_rank_cd(fts_course_details, {to_tsquery}) DESC) as rank_ix
                FROM filtered
                WHERE fts_course_details @@ {to_tsquery} AND approve_status = true
                LIMIT 30
            ),
            result AS (
                SELECT {intermediate_fields}
                FROM fuzzy
                    FULL OUTER JOIN full_text ON fuzzy.id = full_text.id
                    FULL OUTER JOIN partial_search ON coalesce(fuzzy.id, full_text.id) = partial_search.id
                    JOIN filtered ON coalesce(fuzzy.id, full_text.id, partial_search.id) = filtered.id
                ORDER BY
                    coalesce(1.0 / (50 + fuzzy.rank_ix), 0.0) * 1 +
                    coalesce(1.0 / (50 + full_text.rank_ix), 0.0) * 1 +
                    coalesce(1.0 / (50 + partial_search.rank_ix), 0.0) * 1
                DESC
            ) SELECT {search_qp_fields} FROM result",
            search_qp_fields = SEARCH_QP_FIELDS,
            to_tsquery = "to_tsquery('simple', websearch_to_tsquery('simple', $1)::text || ':*')",
            exam_filter = exam_filter,
            intermediate_fields = ADMIN_DASHBOARD_QP_FIELDS.split(", ").map(|field| format!("filtered.{}", field)).collect::<Vec<String>>().join(", ")
        ),
        use_exam_arg
    )
}

/// List of fields in the [`crate::db::models::DBAdminDashboardQP`] to be used with SELECT clauses
pub const ADMIN_DASHBOARD_QP_FIELDS: &str = "id, filelink, from_library, course_code, course_name, year, semester, exam, note, upload_timestamp, approve_status";

/// List of fields in the [`crate::db::models::DBSearchQP`] to be used with SELECT clauses
pub const SEARCH_QP_FIELDS: &str =
    "id, filelink, from_library, course_code, course_name, year, semester, exam, note";

/// Insert a newly uploaded file in the db (and return the id)
/// Parameters in the following order: `course_code`, `course_name`, `year`, `exam`, `semester`, `note`, `filelink`, `from_library`
pub const INSERT_NEW_QP: &str = "INSERT INTO iqps (course_code, course_name, year, exam, semester, note, filelink, from_library) VALUES ($1, $2, $3, $4, $5, $6, $7, $8) RETURNING id";

/// Updates the filelink ($2) of a paper with the given id ($1). Used to update the filelink after a paper is uploaded.
pub const UPDATE_FILELINK: &str = "UPDATE iqps SET filelink=$2 WHERE id=$1";