rustango 0.8.0

//! View-side helpers shared across handlers — model lookup, FK join
//! composition, FK display-value mapping, list-cell rendering, form
//! rendering, and pager URL composition.

use std::collections::HashMap;
use std::fmt::Write as _;

use crate::core::{inventory, FieldSchema, Join, ModelEntry, ModelSchema, Relation};
use crate::sql::sqlx;

use super::render;
use super::templates::render_template;
use super::urls::AppState;

/// Map of `(target_table, source_value_string) → display_value_html`.
/// Populated from joined rows so list/detail rendering needs no extra
/// per-FK queries.
pub(crate) type FkMap = HashMap<(String, String), String>;

/// Resolve `table` to a `ModelSchema`, but only if the admin is configured
/// to expose it. A model that exists but is filtered out via `show_only`
/// returns `None` here, which surfaces to users as a 404 — same response
/// as a genuinely missing table.
pub(crate) fn lookup_model(state: &AppState, table: &str) -> Option<&'static ModelSchema> {
    if !state.is_visible(table) {
        return None;
    }
    inventory::iter::<ModelEntry>
        .into_iter()
        .find(|e| e.schema.table == table)
        .map(|e| e.schema)
}

/// Build one [`Join`] per FK / O2O column on `model` whose target is
/// visible and has a display field. The join's `project` carries only
/// the target's display column — that's all the admin renders.
pub(crate) fn build_fk_joins(state: &AppState, model: &'static ModelSchema) -> Vec<Join> {
    let mut joins = Vec::new();
    for field in model.scalar_fields() {
        let Some(rel) = field.relation else { continue };
        let (to, on) = match rel {
            Relation::Fk { to, on } | Relation::O2O { to, on } => (to, on),
            Relation::M2M { .. } => continue,
        };
        let Some(target) = lookup_model(state, to) else {
            continue;
        };
        let Some(display_field) = target.display_field() else {
            continue;
        };
        joins.push(Join {
            target,
            on_local: field.column,
            on_remote: on,
            // `field.name` is a valid SQL identifier and unique within the
            // model (it's a Rust struct field), so it makes a clean alias.
            alias: field.name,
            project: vec![display_field.column],
        });
    }
    joins
}

/// Walk a row set produced with `joins` set, and for each row build the
/// `(target_table, source_value_string) → display_html` map entry. Rows
/// where the joined display value is `NULL` (LEFT JOIN miss — target row
/// not present) are skipped, so `render_cell` falls back to the raw value.
pub(crate) fn fk_map_from_joined_rows(
    state: &AppState,
    model: &'static ModelSchema,
    rows: &[sqlx::postgres::PgRow],
) -> FkMap {
    let mut map: FkMap = HashMap::new();
    for field in model.scalar_fields() {
        let Some(rel) = field.relation else { continue };
        let to = match rel {
            Relation::Fk { to, .. } | Relation::O2O { to, .. } => to,
            Relation::M2M { .. } => continue,
        };
        let Some(target) = lookup_model(state, to) else {
            continue;
        };
        let Some(display_field) = target.display_field() else {
            continue;
        };
        for row in rows {
            let Some(source) = render::read_value_as_string(row, field) else {
                continue;
            };
            let Some(display) = render::read_joined_value_as_html(row, field.name, display_field)
            else {
                continue;
            };
            map.insert((to.to_owned(), source), display);
        }
    }
    map
}

/// Build a `&q=…&<field>=<v>…` tail for prev/next pager URLs so the
/// active search and filters survive page navigation. Each value is
/// percent-encoded via a tiny ASCII-safe escaper good enough for the
/// admin's expected inputs.
pub(crate) fn pager_suffix(q: Option<&str>, filters: &[(&'static str, String)]) -> String {
    let mut out = String::new();
    if let Some(qs) = q {
        out.push_str("&q=");
        out.push_str(&url_encode(qs));
    }
    for (k, v) in filters {
        out.push('&');
        out.push_str(k);
        out.push('=');
        out.push_str(&url_encode(v));
    }
    out
}

/// Minimal URL-encoder for ASCII inputs. Escapes characters that have
/// special meaning in a query string. Multibyte UTF-8 is percent-encoded
/// byte-by-byte — Postgres handles the bytes the same on the way back.
fn url_encode(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for byte in s.bytes() {
        let safe = byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_' | b'.' | b'~');
        if safe {
            out.push(byte as char);
        } else {
            let _ = write!(out, "%{byte:02X}");
        }
    }
    out
}

/// Render one cell. For FK columns this resolves to a link into the target
/// table; everything else delegates to [`render::render_value`].
pub(crate) fn render_cell(
    row: &sqlx::postgres::PgRow,
    field: &FieldSchema,
    fk_map: &FkMap,
) -> String {
    if let Some(rel) = field.relation {
        let to = match rel {
            Relation::Fk { to, .. } | Relation::O2O { to, .. } => Some(to),
            Relation::M2M { .. } => None,
        };
        if let Some(to) = to {
            let Some(raw_value) = render::read_value_as_string(row, field) else {
                return "<em>NULL</em>".to_owned();
            };
            let raw_esc = render::escape(&raw_value);
            let to_esc = render::escape(to);
            return match fk_map.get(&(to.to_owned(), raw_value)) {
                Some(display) => format!(r#"<a href="/{to_esc}/{raw_esc}">{display}</a>"#),
                // Target hidden by show_only or row genuinely missing — show raw.
                None => raw_esc,
            };
        }
    }
    render::render_value(row, field)
}

/// Render a create or edit form via the `form.html` template. Pre-fill
/// values come from `prefill` (keyed by Rust field name); pass `None` for
/// an empty create form. `pk_locked` makes the PK input read-only (edit
/// mode). `error_msg`, when present, is shown above the form.
pub(crate) fn render_form(
    model: &'static ModelSchema,
    prefill: Option<&HashMap<String, String>>,
    pk_locked: bool,
    error_msg: Option<&str>,
) -> String {
    let action = if pk_locked {
        let pk_field = model.primary_key().expect("pk_locked requires a PK");
        let pk_value = prefill
            .and_then(|m| m.get(pk_field.name).cloned())
            .unwrap_or_default();
        format!("/{}/{}", model.table, render::escape(&pk_value))
    } else {
        format!("/{}", model.table)
    };
    let title = if pk_locked {
        format!("Edit {}", model.name)
    } else {
        format!("New {}", model.name)
    };

    let rows_ctx: Vec<serde_json::Value> = model
        .scalar_fields()
        .map(|f| {
            let value = prefill
                .and_then(|m| m.get(f.name))
                .map_or("", String::as_str);
            let extra = if f.primary_key {
                " <small>(pk)</small>"
            } else if !f.nullable {
                " <small>required</small>"
            } else {
                ""
            };
            serde_json::json!({
                "label": f.name,
                "extra": extra,
                "input": render::render_input(f, value, pk_locked),
            })
        })
        .collect();

    render_template(
        "form.html",
        &serde_json::json!({
            "model": { "name": model.name, "table": model.table },
            "title": title,
            "action": action,
            "error": error_msg,
            "rows": rows_ctx,
        }),
    )
}