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use rayon::prelude::*;
use reqwest::header;
use reqwest::Client;
use reqwest::Url;
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use crate::error::Result;
use crate::tui::markdown;
/// StackExchange API v2.2 URL
// TODO why not https?
const SE_API_URL: &str = "http://api.stackexchange.com";
const SE_API_VERSION: &str = "2.2";
/// Filter generated to include only the fields needed to populate
/// the structs below. Go here to make new filters:
/// [create filter](https://api.stackexchange.com/docs/create-filter).
const SE_FILTER: &str = ".DND5X2VHHUH8HyJzpjo)5NvdHI3w6auG";
/// Pagesize when fetching all SE sites. Should be good for many years...
const SE_SITES_PAGESIZE: u16 = 10000;
/// Represents a StackExchange answer with a custom selection of fields from
/// the [StackExchange docs](https://api.stackexchange.com/docs/types/answer)
#[derive(Clone, Deserialize, Debug)]
pub struct Answer<S> {
#[serde(rename = "answer_id")]
pub id: u32,
pub score: i32,
#[serde(rename = "body_markdown")]
pub body: S,
pub is_accepted: bool,
}
/// Represents a StackExchange question with a custom selection of fields from
/// the [StackExchange docs](https://api.stackexchange.com/docs/types/question)
// TODO container over answers should be generic iterator
#[derive(Clone, Deserialize, Debug)]
pub struct Question<S> {
#[serde(rename = "question_id")]
pub id: u32,
pub score: i32,
#[serde(default = "Vec::new")]
// N.B. empty vector default needed because questions endpoint cannot filter
// answers >= 1
pub answers: Vec<Answer<S>>,
pub title: String,
#[serde(rename = "body_markdown")]
pub body: S,
}
/// Internal struct that represents the boilerplate response wrapper from SE API.
#[derive(Deserialize, Debug)]
struct ResponseWrapper<T> {
items: Vec<T>,
}
#[derive(Deserialize, Serialize, Debug)]
pub struct Site {
pub api_site_parameter: String,
pub site_url: String,
}
#[derive(Clone)]
pub struct Api {
client: Client,
api_key: Option<String>,
}
impl Api {
pub fn new(api_key: Option<String>) -> Self {
// TODO can lazy_static this above
let mut headers = header::HeaderMap::new();
headers.insert(
header::ACCEPT,
header::HeaderValue::from_static("application/json"),
);
let client = Client::builder().default_headers(headers).build().unwrap();
Api { client, api_key }
}
/// Search against the SE site's /questions/{ids} endpoint.
/// Filters out questions with no answers.
pub async fn questions(&self, site: &str, ids: Vec<String>) -> Result<Vec<Question<String>>> {
let total = ids.len().to_string();
let endpoint = format!("questions/{ids}", ids = ids.join(";"));
let qs = self
.client
.get(stackexchange_url(&endpoint))
.query(&self.get_default_se_opts())
.query(&[("site", site), ("pagesize", &total)])
.send()
.await?
.json::<ResponseWrapper<Question<String>>>()
.await?
.items
.into_iter()
.filter(|q| !q.answers.is_empty())
.collect();
Ok(Self::preprocess(qs))
}
/// Search against the SE site's /search/advanced endpoint with a given query.
/// Only fetches questions that have at least one answer.
pub async fn search_advanced(
&self,
query: &str,
site: &str,
limit: u16,
) -> Result<Vec<Question<String>>> {
let qs = self
.client
.get(stackexchange_url("search/advanced"))
.query(&self.get_default_se_opts())
.query(&[
("q", query),
("pagesize", &limit.to_string()),
("site", site),
("answers", "1"),
("order", "desc"),
("sort", "relevance"),
])
.send()
.await?
.json::<ResponseWrapper<Question<String>>>()
.await?
.items;
Ok(Self::preprocess(qs))
}
pub async fn sites(&self) -> Result<Vec<Site>> {
let sites = self
.client
.get(stackexchange_url("sites"))
.query(&[("pagesize", SE_SITES_PAGESIZE.to_string())])
.send()
.await?
.json::<ResponseWrapper<Site>>()
.await?
.items;
Ok(sites
.into_par_iter()
.map(|site| {
let site_url = site.site_url.trim_start_matches("https://").to_string();
Site { site_url, ..site }
})
.collect())
}
fn get_default_se_opts(&self) -> HashMap<&str, &str> {
let mut params = HashMap::new();
params.insert("filter", SE_FILTER);
params.insert("page", "1");
if let Some(key) = &self.api_key {
params.insert("key", key);
}
params
}
/// Sorts answers by score
/// Preprocess SE markdown to "cmark" markdown (or something closer to it)
/// This markdown preprocess _always_ happens.
fn preprocess(qs: Vec<Question<String>>) -> Vec<Question<String>> {
qs.into_par_iter()
.map(|q| {
let mut answers = q.answers;
answers.par_sort_unstable_by_key(|a| -a.score);
let answers = answers
.into_par_iter()
.map(|a| Answer {
body: markdown::preprocess(a.body.clone()),
..a
})
.collect();
Question {
answers,
body: markdown::preprocess(q.body),
..q
}
})
.collect::<Vec<_>>()
}
}
/// Creates stackexchange API url given endpoint
// TODO lazy static this url parse
fn stackexchange_url(path: &str) -> Url {
let mut url = Url::parse(SE_API_URL).unwrap();
url.path_segments_mut()
.unwrap()
.push(SE_API_VERSION)
.extend(path.split('/'));
url
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_stackexchange_url() {
assert_eq!(
stackexchange_url("some/endpoint").as_str(),
"http://api.stackexchange.com/2.2/some/endpoint"
)
}
}
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