package service

import (
	"axolotl/models"
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
)

type apiClient struct {
	base string
	user string
	http *http.Client
}

func (c *apiClient) User() string { return c.user }

func (c *apiClient) do(method, path string, body any) (*http.Response, error) {
	var buf bytes.Buffer
	if body != nil {
		if err := json.NewEncoder(&buf).Encode(body); err != nil {
			return nil, err
		}
	}
	req, err := http.NewRequest(method, c.base+path, &buf)
	if err != nil {
		return nil, err
	}
	if err := c.setAuth(req); err != nil {
		return nil, err
	}
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	return c.http.Do(req)
}

// setAuth attaches either a Bearer token (when a session exists) or the
// X-Ax-User header (no session / non-OIDC servers).
func (c *apiClient) setAuth(req *http.Request) error {
	sess, err := LoadSession()
	if err != nil || sess == nil || sess.Token == "" {
		req.Header.Set("X-Ax-User", c.user)
		return nil
	}
	req.Header.Set("Authorization", "Bearer "+sess.Token)
	return nil
}

func apiDecode[T any](resp *http.Response) (T, error) {
	var v T
	defer resp.Body.Close()
	if resp.StatusCode >= 400 {
		var e struct{ Error string }
		json.NewDecoder(resp.Body).Decode(&e)
		return v, fmt.Errorf("%s", e.Error)
	}
	return v, json.NewDecoder(resp.Body).Decode(&v)
}

func (c *apiClient) GetByID(id string) (*models.Node, error) {
	resp, err := c.do("GET", "/nodes/"+id, nil)
	if err != nil {
		return nil, err
	}
	return apiDecode[*models.Node](resp)
}

func (c *apiClient) List(filter ListFilter) ([]*models.Node, error) {
	q := url.Values{}
	for _, r := range filter.Rels {
		if r.Target == "" {
			q.Add("rel", string(r.Type))
		} else {
			q.Add("rel", string(r.Type)+":"+r.Target)
		}
	}
	path := "/nodes"
	if len(q) > 0 {
		path += "?" + q.Encode()
	}
	resp, err := c.do("GET", path, nil)
	if err != nil {
		return nil, err
	}
	return apiDecode[[]*models.Node](resp)
}

func (c *apiClient) Add(input AddInput) (*models.Node, error) {
	resp, err := c.do("POST", "/nodes", input)
	if err != nil {
		return nil, err
	}
	return apiDecode[*models.Node](resp)
}

func (c *apiClient) Update(id string, input UpdateInput) (*models.Node, error) {
	resp, err := c.do("PATCH", "/nodes/"+id, input)
	if err != nil {
		return nil, err
	}
	return apiDecode[*models.Node](resp)
}

func (c *apiClient) Delete(id string) error {
	resp, err := c.do("DELETE", "/nodes/"+id, nil)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 400 {
		var e struct{ Error string }
		json.NewDecoder(resp.Body).Decode(&e)
		return fmt.Errorf("%s", e.Error)
	}
	return nil
}

func (c *apiClient) ListUsers() ([]*models.Node, error) {
	resp, err := c.do("GET", "/users", nil)
	if err != nil {
		return nil, err
	}
	return apiDecode[[]*models.Node](resp)
}

func (c *apiClient) AddUser(name string) (*models.Node, error) {
	resp, err := c.do("POST", "/users", map[string]string{"name": name})
	if err != nil {
		return nil, err
	}
	return apiDecode[*models.Node](resp)
}