//! The request handlers behind the five table-definition pages.
//!
//! Each page has a GET that renders it and, except for the read-only history,
//! a POST per write it offers. A write answers with its own page's body,
//! re-read from the backend, so what the user sees after a change is the
//! definition as it now is rather than the form they submitted. A refused
//! write answers the same way but with 422 and the backend's own message,
//! which `ui/base.html` swaps in because a 4xx still carries the explanation.
//!
//! Two exceptions. Staging a column changes nothing on the server, so those
//! interactions swap only the column panel. And a successful delete leaves no
//! page to return to — the table it was about is gone — so it redirects to the
//! admin panel instead.

use axum::{
    extract::{Query, State},
    http::{HeaderMap, HeaderValue, StatusCode},
    response::{Html, IntoResponse, Redirect, Response},
};
use axum_extra::extract::Form;

use crate::{
    AppState,
    definitions::table_definition::{
        AddTableColumnsRequest, CopyProfileRequest, CreateInvoiceTemplateTableRequest,
        DeleteTableRequest, RenameColumnAliasRequest,
    },
    schema::{ColumnForm, proto_columns},
    services::{authenticated_request, reject_cross_site},
};

use super::{
    loader::{self, load_page},
    state::{
        CopyForm, DeleteForm, GeneratedTableView, InvoiceTemplateForm, LoadError, PageInputs,
        RenameForm, Selection, TableDefinitionPageState,
    },
    ui,
};

/// Which page a response belongs to: what the switcher marks as current, and
/// which fragment a write on it swaps back.
#[derive(Clone, Copy)]
enum Page {
    Columns,
    Delete,
    Copy,
    Template,
    History,
}

impl Page {
    fn name(self) -> &'static str {
        match self {
            Self::Columns => "columns",
            Self::Delete => "delete",
            Self::Copy => "copy",
            Self::Template => "template",
            Self::History => "history",
        }
    }

    fn render_page(self, page: &TableDefinitionPageState) -> String {
        match self {
            Self::Columns => ui::render_columns_page(page),
            Self::Delete => ui::render_delete_page(page),
            Self::Copy => ui::render_copy_page(page),
            Self::Template => ui::render_template_page(page),
            Self::History => ui::render_history_page(page),
        }
    }

    /// The `#table-panel` swap. History has no writes, so it never asks.
    fn render_fragment(self, page: &TableDefinitionPageState) -> String {
        match self {
            Self::Columns => ui::render_columns_fragment(page),
            Self::Delete => ui::render_delete_fragment(page),
            Self::Copy => ui::render_copy_fragment(page),
            Self::Template => ui::render_template_fragment(page),
            Self::History => ui::render_history_page(page),
        }
    }
}

// ── The pages ───────────────────────────────────────────────────────────────

/// GET /admin/tables/columns
pub(crate) async fn columns_page(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
) -> Response {
    show(state, headers, PageInputs::for_selection(selection), Page::Columns).await
}

/// GET /admin/tables/delete
pub(crate) async fn delete_page(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
) -> Response {
    show(state, headers, PageInputs::for_selection(selection), Page::Delete).await
}

/// GET /admin/profiles/copy
pub(crate) async fn copy_page(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
) -> Response {
    show(state, headers, profile_inputs(selection), Page::Copy).await
}

/// GET /admin/tables/from-template
pub(crate) async fn template_page(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
) -> Response {
    show(state, headers, profile_inputs(selection), Page::Template).await
}

/// GET /admin/profiles/history
pub(crate) async fn history_page(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
) -> Response {
    show(state, headers, PageInputs::for_selection(selection), Page::History).await
}

/// The profile-wide pages act on a profile, so a table in the query is
/// dropped rather than carried into a form that has no use for it.
fn profile_inputs(selection: Selection) -> PageInputs {
    PageInputs::for_selection(Selection {
        profile: selection.profile,
        table: String::new(),
    })
}

async fn show(state: AppState, headers: HeaderMap, inputs: PageInputs, page: Page) -> Response {
    match load_page(state, &headers, inputs).await {
        Ok(mut loaded) => {
            loaded.active = page.name();
            Html(page.render_page(&loaded)).into_response()
        }
        Err(error) => load_error_response(error),
    }
}

// ── The writes ──────────────────────────────────────────────────────────────

/// POST /admin/tables/columns/builder — staging a column to append.
///
/// Nothing is written here; the panel is swapped back with the column added,
/// removed, or its index toggled, exactly as the Add-table builder works.
pub(crate) async fn update_columns(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
    Form(form): Form<ColumnForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    // Staging a column applies the vocabulary's rules, so it is read before
    // the panel is rebuilt; `load_page` reuses what is read here.
    let mut definitions = state.definitions.clone();
    let catalog = match loader::load_column_catalog(&mut definitions, &headers).await {
        Ok(catalog) => catalog,
        Err(error) => return load_error_response(error),
    };

    let mut inputs = PageInputs::for_selection(selection);
    inputs.columns = form.to_draft(catalog, false);

    let index = form.index.unwrap_or(0);
    match form.action.as_str() {
        "add-column" => match inputs.columns.add_from_inputs() {
            Ok(status) => inputs.status = Some(status),
            Err(message) => inputs.error = Some(message),
        },
        "remove-column" => {
            if let Err(message) = inputs.columns.remove(index) {
                inputs.error = Some(message);
            }
        }
        "toggle-index" => inputs.columns.toggle_indexed(index),
        _ => {}
    }

    match load_page(state, &headers, inputs).await {
        Ok(mut loaded) => {
            loaded.active = Page::Columns.name();
            Html(ui::render_column_panel(&loaded)).into_response()
        }
        Err(error) => load_error_response(error),
    }
}

/// POST /admin/tables/columns — AddTableColumns.
pub(crate) async fn add_columns(
    State(state): State<AppState>,
    headers: HeaderMap,
    Query(selection): Query<Selection>,
    Form(form): Form<ColumnForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    // The draft is validated before the write, so the vocabulary it is held to
    // is read first; `load_page` reuses what is read here.
    let mut definitions = state.definitions.clone();
    let catalog = match loader::load_column_catalog(&mut definitions, &headers).await {
        Ok(catalog) => catalog,
        Err(error) => return load_error_response(error),
    };

    let mut inputs = PageInputs::for_selection(selection);
    inputs.columns = form.to_draft(catalog.clone(), false);

    if !inputs.selection.has_table() {
        return refuse(state, headers, inputs, Page::Columns, "Select a table first.".to_string())
            .await;
    }
    if inputs.columns.is_empty() {
        return refuse(
            state,
            headers,
            inputs,
            Page::Columns,
            "Describe at least one column before adding.".to_string(),
        )
        .await;
    }
    // The same checks the server runs, applied to a draft that may have been
    // rebuilt from a posted form rather than through the panel.
    if let Err(message) = inputs.columns.validate() {
        return refuse(state, headers, inputs, Page::Columns, message).await;
    }

    let request = AddTableColumnsRequest {
        profile_name: inputs.selection.profile.clone(),
        table_name: inputs.selection.table.clone(),
        columns: proto_columns(&inputs.columns.added),
        indexes: inputs.columns.selected_index_names(),
        // The append panel names its columns itself; the only generated ones it
        // can produce are the phone and IBAN companions, which it does not
        // offer to rename. The table's own rename form is where that is done.
        generated_aliases: Vec::new(),
    };
    let Ok(request) = authenticated_request(&headers, request) else {
        return Redirect::to("/login").into_response();
    };

    match definitions.add_table_columns(request).await {
        Ok(response) if response.get_ref().success => {
            let added = inputs.columns.added.len();
            inputs.sql = Some(response.into_inner().sql);
            inputs.status = Some(format!(
                "{added} column{} added to `{}`.",
                if added == 1 { "" } else { "s" },
                inputs.selection.table
            ));
            // The columns are the table's now, so the panel starts empty.
            inputs.columns = crate::schema::ColumnDraft::for_append(catalog);
            respond(state, headers, inputs, Page::Columns, StatusCode::OK).await
        }
        Ok(response) => {
            let message = response.into_inner().sql;
            let message = if message.is_empty() {
                "The backend did not add the columns.".to_string()
            } else {
                message
            };
            refuse(state, headers, inputs, Page::Columns, message).await
        }
        Err(error) => {
            refuse(state, headers, inputs, Page::Columns, error.message().to_string()).await
        }
    }
}

/// POST /admin/tables/rename — RenameColumnAlias.
pub(crate) async fn rename_column(
    State(state): State<AppState>,
    headers: HeaderMap,
    Form(form): Form<RenameForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    let mut inputs = PageInputs::for_selection(Selection {
        profile: form.profile.clone(),
        table: form.table.clone(),
    });
    inputs.rename = form.clone();

    if form.old_column_name.is_empty() || form.new_column_name.trim().is_empty() {
        return refuse(
            state,
            headers,
            inputs,
            Page::Columns,
            "Choose a column and type its new name.".to_string(),
        )
        .await;
    }

    let request = RenameColumnAliasRequest {
        profile_name: form.profile.clone(),
        table_name: form.table.clone(),
        old_column_name: form.old_column_name.clone(),
        new_column_name: form.new_column_name.trim().to_string(),
    };
    let Ok(request) = authenticated_request(&headers, request) else {
        return Redirect::to("/login").into_response();
    };

    let mut definitions = state.definitions.clone();
    match definitions.rename_column_alias(request).await {
        Ok(response) if response.get_ref().success => {
            inputs.status = Some(response.into_inner().message);
            inputs.rename = RenameForm {
                profile: form.profile,
                table: form.table,
                ..Default::default()
            };
            respond(state, headers, inputs, Page::Columns, StatusCode::OK).await
        }
        Ok(response) => {
            let message = response.into_inner().message;
            let message = if message.is_empty() {
                "The backend did not rename the column.".to_string()
            } else {
                message
            };
            refuse(state, headers, inputs, Page::Columns, message).await
        }
        Err(error) => {
            refuse(state, headers, inputs, Page::Columns, error.message().to_string()).await
        }
    }
}

/// POST /admin/tables/delete — DeleteTable.
///
/// On success there is nothing left for this page to show, so it hands the
/// browser to the admin panel with the profile still selected.
pub(crate) async fn delete_table(
    State(state): State<AppState>,
    headers: HeaderMap,
    Form(form): Form<DeleteForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    let inputs = PageInputs::for_selection(Selection {
        profile: form.profile.clone(),
        table: form.table.clone(),
    });

    // The typed name is the whole guard: the drop is CASCADE, and it takes the
    // profile with it when this was its last table.
    if form.confirm_table_name.trim() != form.table || form.table.is_empty() {
        return refuse(
            state,
            headers,
            inputs,
            Page::Delete,
            "Type the table's name exactly to confirm the deletion.".to_string(),
        )
        .await;
    }

    let request = DeleteTableRequest {
        profile_name: form.profile.clone(),
        table_name: form.table.clone(),
    };
    let Ok(request) = authenticated_request(&headers, request) else {
        return Redirect::to("/login").into_response();
    };

    let mut definitions = state.definitions.clone();
    match definitions.delete_table(request).await {
        Ok(response) if response.get_ref().success => {
            // The profile may have gone with it, in which case the admin panel
            // refuses the selection; landing on the bare panel is what the
            // caller wants then anyway.
            let location = format!("/admin?profile={}", form.profile);
            match HeaderValue::try_from(location) {
                Ok(location) => {
                    let mut response = Html(String::new()).into_response();
                    response.headers_mut().insert("hx-redirect", location);
                    response
                }
                Err(_) => (StatusCode::INTERNAL_SERVER_ERROR, "Invalid redirect").into_response(),
            }
        }
        Ok(response) => {
            let message = response.into_inner().message;
            let message = if message.is_empty() {
                "The backend did not delete the table.".to_string()
            } else {
                message
            };
            refuse(state, headers, inputs, Page::Delete, message).await
        }
        Err(error) => {
            refuse(state, headers, inputs, Page::Delete, error.message().to_string()).await
        }
    }
}

/// POST /admin/profiles/copy — CopyProfile.
pub(crate) async fn copy_profile(
    State(state): State<AppState>,
    headers: HeaderMap,
    Form(form): Form<CopyForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    let mut inputs = PageInputs::for_selection(Selection {
        profile: form.profile.clone(),
        table: String::new(),
    });
    inputs.copy = form.clone();

    if form.target_profile_name.trim().is_empty() {
        return refuse(
            state,
            headers,
            inputs,
            Page::Copy,
            "Name the profile to copy into.".to_string(),
        )
        .await;
    }

    let request = CopyProfileRequest {
        source_profile_name: form.profile.clone(),
        target_profile_name: form.target_profile_name.trim().to_string(),
        table_names: form.table_names.clone(),
    };
    let Ok(request) = authenticated_request(&headers, request) else {
        return Redirect::to("/login").into_response();
    };

    let mut definitions = state.definitions.clone();
    match definitions.copy_profile(request).await {
        Ok(response) if response.get_ref().success => {
            let response = response.into_inner();
            inputs.status = Some(format!(
                "{} — {} table(s) and {} script(s) copied.",
                response.message, response.tables_copied, response.scripts_copied
            ));
            inputs.copy = CopyForm {
                profile: form.profile,
                ..Default::default()
            };
            respond(state, headers, inputs, Page::Copy, StatusCode::OK).await
        }
        Ok(response) => {
            let message = response.into_inner().message;
            let message = if message.is_empty() {
                "The backend did not copy the profile.".to_string()
            } else {
                message
            };
            refuse(state, headers, inputs, Page::Copy, message).await
        }
        Err(error) => refuse(state, headers, inputs, Page::Copy, error.message().to_string()).await,
    }
}

/// POST /admin/tables/from-template — CreateInvoiceTemplateTable.
pub(crate) async fn create_from_invoice_template(
    State(state): State<AppState>,
    headers: HeaderMap,
    Form(form): Form<InvoiceTemplateForm>,
) -> Response {
    if let Some(rejection) = reject_cross_site(&headers) {
        return rejection;
    }

    let mut inputs = PageInputs::for_selection(Selection {
        profile: form.profile.clone(),
        table: String::new(),
    });
    inputs.invoice = form.clone();

    if form.table_name.trim().is_empty() || form.typst_source.trim().is_empty() {
        return refuse(
            state,
            headers,
            inputs,
            Page::Template,
            "A table name and the template's source are both required.".to_string(),
        )
        .await;
    }

    let request = CreateInvoiceTemplateTableRequest {
        profile_name: form.profile.clone(),
        table_name: form.table_name.trim().to_string(),
        typst_source: form.typst_source.clone(),
        row_display_columns: form.display_columns(),
    };
    let Ok(request) = authenticated_request(&headers, request) else {
        return Redirect::to("/login").into_response();
    };

    let mut definitions = state.definitions.clone();
    match definitions.create_invoice_template_table(request).await {
        Ok(response) if response.get_ref().success => {
            let response = response.into_inner();
            inputs.status = Some(format!(
                "{} table(s) created from the template.",
                response.tables.len()
            ));
            inputs.generated = response
                .tables
                .into_iter()
                .map(|table| GeneratedTableView {
                    table_name: table.table_name,
                    collection_path: table.collection_path,
                    parent_table_name: table.parent_table_name,
                })
                .collect();
            inputs.invoice = InvoiceTemplateForm {
                profile: form.profile,
                ..Default::default()
            };
            respond(state, headers, inputs, Page::Template, StatusCode::OK).await
        }
        Ok(_) => {
            refuse(
                state,
                headers,
                inputs,
                Page::Template,
                "The backend did not create the template's tables.".to_string(),
            )
            .await
        }
        Err(error) => {
            refuse(state, headers, inputs, Page::Template, error.message().to_string()).await
        }
    }
}

/// Re-reads the page's body and answers with it.
async fn respond(
    state: AppState,
    headers: HeaderMap,
    inputs: PageInputs,
    page: Page,
    status: StatusCode,
) -> Response {
    match load_page(state, &headers, inputs).await {
        Ok(mut loaded) => {
            loaded.active = page.name();
            (status, Html(page.render_fragment(&loaded))).into_response()
        }
        Err(error) => load_error_response(error),
    }
}

/// Answers a refused write: the page as it still is, plus the reason.
async fn refuse(
    state: AppState,
    headers: HeaderMap,
    mut inputs: PageInputs,
    page: Page,
    message: String,
) -> Response {
    inputs.error = Some(message);
    respond(state, headers, inputs, page, StatusCode::UNPROCESSABLE_ENTITY).await
}

fn load_error_response(error: LoadError) -> Response {
    match error {
        LoadError::Unauthenticated => Redirect::to("/login").into_response(),
        LoadError::Forbidden => (
            StatusCode::FORBIDDEN,
            Html(ui::render_load_error(
                "Table-management permission is required.",
            )),
        )
            .into_response(),
        LoadError::Backend(message) => (
            StatusCode::BAD_GATEWAY,
            Html(ui::render_load_error(&message)),
        )
            .into_response(),
    }
}