//! Conversion of a parsed OpenAPI document into a cielago [`Collection`].

use std::collections::HashSet;

use serde_json::Value;

use super::docs::{body_docs, param_doc, response_docs};

use super::examples::example_for_schema;

use super::resolve::deref;

use crate::model::{AuthStyle, Collection, KeyValueRow, Method, OAuthConfig, SavedRequest};

const METHODS: [&str; 7] = ["get", "post", "put", "patch", "delete", "head", "options"];

pub fn import_spec(doc: &Value, name: &str, source: Option<String>) -> Collection {

    let mut collection = Collection::new(name);

    collection.spec_source = source;

    if let Some(servers) = doc.get("servers").and_then(Value::as_array) {

        for s in servers {

            if let Some(url) = s.get("url").and_then(Value::as_str) {

                let url = url.trim_end_matches('/').to_string();

                if !url.is_empty() && !collection.servers.contains(&url) {

                    collection.servers.push(url);

                }

            }

        }

    }

    collection.auth = extract_oauth(doc);

    if let Some(paths) = doc.get("paths").and_then(Value::as_object) {

        for (path, item) in paths {

            let item = deref(doc, item);

            let path_level_params = item.get("parameters").and_then(Value::as_array);

            for method in METHODS {

                let Some(op) = item.get(method) else { continue };

                collection

                    .requests

                    .push(build_request(doc, path, method, path_level_params, op));

            }

        }

    }

    collection

}

/// Find the first `oauth2` security scheme with a clientCredentials flow and

/// prefill token URL + scopes (credentials are filled in by the user).

fn extract_oauth(doc: &Value) -> Option<OAuthConfig> {

    let schemes = doc.get("components")?.get("securitySchemes")?.as_object()?;

    for (_, scheme) in schemes {

        let scheme = deref(doc, scheme);

        if scheme.get("type").and_then(Value::as_str) != Some("oauth2") {

            continue;

        }

        let Some(flow) = scheme.get("flows").and_then(|f| f.get("clientCredentials")) else {

            continue;

        };

        let token_url = flow

            .get("tokenUrl")

            .and_then(Value::as_str)

            .unwrap_or_default()

            .to_string();

        let scopes = flow

            .get("scopes")

            .and_then(Value::as_object)

            .map(|o| o.keys().cloned().collect())

            .unwrap_or_default();

        return Some(OAuthConfig {

            token_url,

            scopes,

            auth_style: AuthStyle::Basic,

            ..Default::default()

        });

    }

    None

}

fn build_request(

    doc: &Value,

    path: &str,

    method: &str,

    path_level_params: Option<&Vec<Value>>,

    op: &Value,

) -> SavedRequest {

    let summary = op

        .get("summary")

        .and_then(Value::as_str)

        .filter(|s| !s.trim().is_empty())

        .map(str::to_string);

    let operation_id = op

        .get("operationId")

        .and_then(Value::as_str)

        .filter(|s| !s.trim().is_empty())

        .map(str::to_string);

    // `summary` first: it's the human-readable descriptor. `operationId` is

    // often a long generated controller name.

    let name = summary

        .clone()

        .or_else(|| operation_id.clone())

        .unwrap_or_else(|| format!("{} {}", method.to_uppercase(), path));

    let mut req = SavedRequest::blank(name);

    req.summary = summary;

    req.operation_id = operation_id;

    req.description = op

        .get("description")

        .and_then(Value::as_str)

        .map(str::trim)

        .filter(|s| !s.is_empty())

        .map(str::to_string);

    req.method = Method::parse(method).unwrap_or(Method::Get);

    req.path = path.to_string();

    req.tags = op

        .get("tags")

        .and_then(Value::as_array)

        .map(|a| {

            a.iter()

                .filter_map(Value::as_str)

                .map(String::from)

                .collect()

        })

        .unwrap_or_default();

    // Merge operation-level and path-level parameters; operation wins on

    // duplicate (name, in) pairs.

    let mut merged: Vec<&Value> = Vec::new();

    let mut seen: HashSet<(String, String)> = HashSet::new();

    let op_params = op.get("parameters").and_then(Value::as_array);

    for p in op_params.into_iter().flatten() {

        let p = deref(doc, p);

        let key = param_key(p);

        seen.insert(key);

        merged.push(p);

    }

    for p in path_level_params.into_iter().flatten() {

        let p = deref(doc, p);

        if seen.insert(param_key(p)) {

            merged.push(p);

        }

    }

    for p in merged {

        let name = p.get("name").and_then(Value::as_str).unwrap_or_default();

        if name.is_empty() {

            continue;

        }

        let required = p.get("required").and_then(Value::as_bool).unwrap_or(false);

        let location = p.get("in").and_then(Value::as_str).unwrap_or("");

        let value = param_value(doc, p, required);

        match location {

            "path" => req.path_params.push(KeyValueRow::new(name, value, true)),

            "query" => req.query.push(KeyValueRow::new(name, value, required)),

            "header" => req.headers.push(KeyValueRow::new(name, value, required)),

            _ => continue, // cookies etc. unsupported in v1

        }

        req.docs.push(param_doc(doc, p));

    }

    // Headers the spec implies without listing them as `in: header` params.

    // Explicit params win on a name collision.

    for row in implied_headers(doc, op) {

        if !req

            .headers

            .iter()

            .any(|h| h.key.eq_ignore_ascii_case(&row.key))

        {

            req.headers.push(row);

        }

    }

    req.body = extract_body(doc, op);

    if let Some(schema) = body_media(doc, op).and_then(|m| m.get("schema")) {

        req.docs.extend(body_docs(doc, schema));

    }

    if let Some(content) = success_response_content(doc, op)

        && let Some((_, media)) = pick_media(content)

        && let Some(schema) = media.get("schema")

    {

        req.docs.extend(response_docs(doc, schema));

    }

    req

}

/// Headers an operation carries by definition rather than by parameter: the

/// media type it consumes, the one it produces, and any apiKey-in-header

/// security scheme it requires. API-key rows arrive disabled — the value is

/// the user's to supply.

fn implied_headers(doc: &Value, op: &Value) -> Vec<KeyValueRow> {

    let mut out = Vec::new();

    if let Some(ct) = request_media_type(doc, op) {

        out.push(KeyValueRow::new("Content-Type", ct, true));

    }

    if let Some(accept) = response_media_type(doc, op) {

        out.push(KeyValueRow::new("Accept", accept, true));

    }

    for name in api_key_headers(doc, op) {

        out.push(KeyValueRow::new(name, "", false));

    }

    out

}

fn request_media_type(doc: &Value, op: &Value) -> Option<String> {

    let rb = deref(doc, op.get("requestBody")?);

    let content = rb.get("content").and_then(Value::as_object)?;

    pick_media(content).map(|(k, _)| k.clone())

}

/// Media type from the first success response (or `default`), so `Accept`

/// matches what the endpoint actually returns.

fn response_media_type(doc: &Value, op: &Value) -> Option<String> {

    let content = success_response_content(doc, op)?;

    pick_media(content).map(|(k, _)| k.clone())

}

/// The `content` map of the first success response (or `default`) — the shape

/// the endpoint returns, used for both the `Accept` header and response docs.

fn success_response_content<'a>(

    doc: &'a Value,

    op: &'a Value,

) -> Option<&'a serde_json::Map<String, Value>> {

    let responses = op.get("responses").and_then(Value::as_object)?;

    let resp = responses

        .iter()

        .find(|(code, _)| code.starts_with('2'))

        .or_else(|| {

            responses

                .iter()

                .find(|(code, _)| code.as_str() == "default")

        })

        .map(|(_, v)| v)?;

    deref(doc, resp).get("content").and_then(Value::as_object)

}

/// Header names from apiKey security schemes this operation requires,

/// preferring operation-level `security` over the document default.

fn api_key_headers(doc: &Value, op: &Value) -> Vec<String> {

    let Some(requirements) = op

        .get("security")

        .or_else(|| doc.get("security"))

        .and_then(Value::as_array)

    else {

        return Vec::new();

    };

    let Some(schemes) = doc

        .get("components")

        .and_then(|c| c.get("securitySchemes"))

        .and_then(Value::as_object)

    else {

        return Vec::new();

    };

    let mut out: Vec<String> = Vec::new();

    for requirement in requirements {

        let Some(obj) = requirement.as_object() else {

            continue;

        };

        for scheme_name in obj.keys() {

            let Some(scheme) = schemes.get(scheme_name) else {

                continue;

            };

            let scheme = deref(doc, scheme);

            if scheme.get("type").and_then(Value::as_str) != Some("apiKey")

                || scheme.get("in").and_then(Value::as_str) != Some("header")

            {

                continue;

            }

            if let Some(name) = scheme.get("name").and_then(Value::as_str)

                && !name.is_empty()

                && !out.iter().any(|e| e.eq_ignore_ascii_case(name))

            {

                out.push(name.to_string());

            }

        }

    }

    out

}

fn param_key(p: &Value) -> (String, String) {

    (

        p.get("name")

            .and_then(Value::as_str)

            .unwrap_or_default()

            .into(),

        p.get("in")

            .and_then(Value::as_str)

            .unwrap_or_default()

            .into(),

    )

}

/// Value for a parameter. Required params fall back to type-based stubs so the

/// request is sendable out of the box; optional params only get explicitly

/// authored examples/defaults (otherwise empty).

fn param_value(doc: &Value, p: &Value, required: bool) -> String {

    if let Some(v) = explicit_param_value(doc, p) {

        return v;

    }

    if !required {

        return String::new();

    }

    match p.get("schema") {

        Some(schema) => value_to_string(&example_for_schema(doc, deref(doc, schema))),

        None => String::new(),

    }

}

/// Explicitly authored example/default on the parameter or its schema.

fn explicit_param_value(doc: &Value, p: &Value) -> Option<String> {

    if let Some(ex) = p.get("example") {

        return Some(value_to_string(ex));

    }

    if let Some(exs) = p.get("examples").and_then(Value::as_object)

        && let Some((_, first)) = exs.iter().next()

    {

        let first = deref(doc, first);

        if let Some(v) = first.get("value") {

            return Some(value_to_string(v));

        }

    }

    let schema = deref(doc, p.get("schema")?);

    if let Some(ex) = schema.get("example") {

        return Some(value_to_string(ex));

    }

    if let Some(def) = schema.get("default") {

        return Some(value_to_string(def));

    }

    None

}

/// Request body from `requestBody`, preferring JSON media types; falls back to

/// a schema-generated example so payloads are always populated and editable.

fn extract_body(doc: &Value, op: &Value) -> Option<String> {

    let media = body_media(doc, op)?;

    if let Some(ex) = media.get("example") {

        return Some(body_to_string(ex));

    }

    if let Some(exs) = media.get("examples").and_then(Value::as_object)

        && let Some((_, first)) = exs.iter().next()

    {

        let first = deref(doc, first);

        if let Some(v) = first.get("value") {

            return Some(body_to_string(v));

        }

    }

    let schema = media.get("schema")?;

    Some(body_to_string(&example_for_schema(doc, schema)))

}

/// The media-type entry of `requestBody` that cielago sends — and therefore

/// the one both the generated body and the Docs tab describe.

fn body_media<'a>(doc: &'a Value, op: &'a Value) -> Option<&'a Value> {

    let rb = deref(doc, op.get("requestBody")?);

    let content = rb.get("content").and_then(Value::as_object)?;

    pick_media(content).map(|(_, media)| media)

}

/// Preferred entry from a `content` map: JSON first, then anything JSON-ish,

/// then whatever the spec listed first.

fn pick_media(content: &serde_json::Map<String, Value>) -> Option<(&String, &Value)> {

    content

        .iter()

        .find(|(k, _)| k.as_str() == "application/json")

        .or_else(|| content.iter().find(|(k, _)| k.contains("json")))

        .or_else(|| content.iter().next())

}

fn value_to_string(v: &Value) -> String {

    match v {

        Value::String(s) => s.clone(),

        other => serde_json::to_string(other).unwrap_or_default(),

    }

}

fn body_to_string(v: &Value) -> String {

    match v {

        Value::String(s) => s.clone(),

        other => serde_json::to_string_pretty(other).unwrap_or_default(),

    }

}