Add provider info functions to the FFI API

A lot of work from @Hocuri and @Simon-Laux mostly.

This exposes the API of the deltachat-provider-overview crate on the
deltachat FFI API, allowing clients to use it to help users set up
their accounts.

deltachat-ffi/src/lib.rs

@@ -2813,6 +2813,8 @@ fn as_opt_str<'a>(s: *const libc::c_char) -> Option<&'a str> {
     Some(dc_tools::as_str(s))
 }
 
+pub mod providers;
+
 pub trait ResultExt<T> {
     fn unwrap_or_log_default(self, context: &context::Context, message: &str) -> T;
     fn log_err(&self, context: &context::Context, message: &str);

deltachat-ffi/src/providers.rs

@@ -0,0 +1,92 @@
+extern crate deltachat_provider_overview;
+
+use std::ptr;
+
+use deltachat::dc_tools::{as_str, StrExt};
+use deltachat_provider_overview::StatusState;
+
+#[no_mangle]
+pub type dc_provider_t = deltachat_provider_overview::Provider;
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_new_from_domain(
+    domain: *const libc::c_char,
+) -> *const dc_provider_t {
+    match deltachat_provider_overview::get_provider_info(as_str(domain)) {
+        Some(provider) => provider,
+        None => ptr::null(),
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_new_from_email(
+    email: *const libc::c_char,
+) -> *const dc_provider_t {
+    let domain = deltachat_provider_overview::get_domain_from_email(as_str(email));
+    match deltachat_provider_overview::get_provider_info(domain) {
+        Some(provider) => provider,
+        None => ptr::null(),
+    }
+}
+
+macro_rules! null_guard {
+    ($context:tt) => {
+        if $context.is_null() {
+            return ptr::null_mut() as *mut libc::c_char;
+        }
+    };
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_get_overview_page(
+    provider: *const dc_provider_t,
+) -> *mut libc::c_char {
+    null_guard!(provider);
+    format!(
+        "{}/{}",
+        deltachat_provider_overview::PROVIDER_OVERVIEW_URL,
+        (*provider).overview_page
+    )
+    .strdup()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_get_name(provider: *const dc_provider_t) -> *mut libc::c_char {
+    null_guard!(provider);
+    (*provider).name.strdup()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_get_markdown(
+    provider: *const dc_provider_t,
+) -> *mut libc::c_char {
+    null_guard!(provider);
+    (*provider).markdown.strdup()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_get_status_date(
+    provider: *const dc_provider_t,
+) -> *mut libc::c_char {
+    null_guard!(provider);
+    (*provider).status.date.strdup()
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_get_status(provider: *const dc_provider_t) -> u32 {
+    if provider.is_null() {
+        return 0;
+    }
+    match (*provider).status.state {
+        StatusState::OK => 1,
+        StatusState::PREPARATION => 2,
+        StatusState::BROKEN => 3,
+    }
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn dc_provider_unref(_provider: *const dc_provider_t) {
+    ()
+}
+
+// TODO expose general provider overview url?