/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at https://mozilla.org/MPL/2.0/.
 */
package main

import (
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"

	dp "idio.link/go/depager/v2"
)

func NewGogsClient(
	ctx context.Context,
	accessToken string,
) *GogsClient {
	t := &http.Transport{
		TLSClientConfig:       &tls.Config{InsecureSkipVerify: false},
		TLSHandshakeTimeout:   15 * time.Second,
		IdleConnTimeout:       30 * time.Minute,
		ResponseHeaderTimeout: 180 * time.Second,
		ExpectContinueTimeout: 10 * time.Second,
	}
	c := &http.Client{
		Transport: t,
		Timeout:   30 * time.Minute,
	}
	baseURI, _ := url.Parse("https://git.idiolink.net/api/v1/")

	return &GogsClient{
		baseURI:    baseURI,
		ctx:        ctx,
		httpClient: c,
		retries:    3,
		retryWait:  10 * time.Second,
		token:      accessToken,
	}
}

type GogsClient struct {
	ctx             context.Context
	httpClient      *http.Client
	baseURI         *url.URL
	blockReqsBefore time.Time
	retries         int
	retryWait       time.Duration
	token           string
}

func (c *GogsClient) expandResource(
	resource *url.URL,
) *url.URL {
	ex, err :=
		url.JoinPath(c.baseURI.String(), resource.EscapedPath())
	if err != nil {
		panic(fmt.Sprintf("BUG: gogs client: expand resource: failed to join path: '%s' + '%s': %v", c.baseURI, resource.RequestURI(), err))
	}
	next, err := url.Parse(ex)
	if err != nil {
		panic(fmt.Sprintf("BUG: gogs client: expand resource: failed to parse expanded resource '%s': %v", ex, err))
	}
	return next
}

func (c *GogsClient) sendRequestWithRetry(
	req *http.Request,
) (resp *http.Response, err error) {
	for i := 0; i < c.retries+1; i++ {
		resp, err = c.httpClient.Do(req)
		if err != nil {
			err = fmt.Errorf("send request with retry: %w", err)
			return
		}
	}
	if resp == nil {
		err = fmt.Errorf("send request with retry: unknown failure")
		return
	}
	return
}

func (c *GogsClient) request(
	method string,
	resource *url.URL,
	body io.Reader,
) (respHead http.Header, respBody []byte, err error) {
	req, err := http.NewRequestWithContext(
		c.ctx,
		method,
		resource.String(),
		body,
	)
	if err != nil {
		err = fmt.Errorf("request %#v: %w", resource.String(), err)
		return
	}
	req.Header.
		Add("Authorization", fmt.Sprintf("token %s", c.token))

	resp, err := c.sendRequestWithRetry(req)
	if err != nil {
		err = fmt.Errorf("request %#v: %+v: %w", req.URL.String(), req, err)
		return
	}
	defer resp.Body.Close()

	respHead = resp.Header
	respBody, err = io.ReadAll(resp.Body)
	if err != nil {
		err = fmt.Errorf("request %v: failed to read response body: %w", resource, err)
		return
	}

	// Success response
	if 200 <= resp.StatusCode && resp.StatusCode <= 299 {
		return
	}

	err = fmt.Errorf("request %v: %s", resource, http.StatusText(resp.StatusCode))
	return
}

func (c *GogsClient) get(
	resource *url.URL,
) (http.Header, []byte, error) {
	return c.request(http.MethodGet, resource, nil)
}

func newGogsSubclient[T any](
	c *GogsClient,
	resource *url.URL,
) *GogsSubclient[T] {
	expanded := c.expandResource(resource)
	return &GogsSubclient[T]{
		GogsClient: *c,
		uri:        expanded,
	}
}

type GogsSubclient[T any] struct {
	GogsClient

	uri *url.URL
}

func (c *GogsSubclient[T]) NextPage(
	offset uint64,
) (page dp.Page[T], _ uint64, err error) {
	aggr := make([]T, 0, 32)
	head, body, err := c.get(c.uri)
	if err != nil {
		err = fmt.Errorf("gogs client: next page: %w", err)
		return
	}
	err = json.Unmarshal(body, &aggr)
	if err != nil {
		err = fmt.Errorf("gogs client: next page: unmarshal response: %w", err)
		return
	}
	if next := getLinkNext(head.Get("link")); next != "" {
		c.uri, err = url.Parse(next)
		if err != nil {
			err = fmt.Errorf("gogs client: next page: unable to parse next link '%s': %w", next, err)
			return
		}
	}
	page = GogsAggregate[T](aggr)
	return
}

type GogsAggregate[T any] []T

func (a GogsAggregate[T]) Elems() []T {
	return a
}

type GogsRepo struct {
	FullName  string `json:"full_name"`
	CloneURL  string `json:"clone_url"`
	HTMLURL   string `json:"html_url"`
	DefBranch string `json:"default_branch"`
}

func (r *GogsRepo) Path() string {
	return r.FullName
}

func (r *GogsRepo) GitURI() string {
	return r.CloneURL
}

func (r *GogsRepo) WebURI() string {
	return r.HTMLURL
}

func (r *GogsRepo) DefaultBranch() string {
	return r.DefBranch
}

func FetchOrgRepos[T *GogsRepo](
	c *GogsClient,
	group string,
) dp.Pager[T] {
	resStrFmt := "/orgs/%s/repos"
	escaped := url.PathEscape(group)
	resStr := fmt.Sprintf(resStrFmt, escaped)

	resource, err := url.Parse(resStr)
	if err != nil { // should only occur in case of bugs
		panic(err)
	}
	return dp.NewPager[T](
		newGogsSubclient[T](c, resource),
		100,
	)
}

type GogsTag struct {
	Name string `json:"name"`
	Commit struct {
		Timestamp string `json:"timestamp"`
	} `json:"commit"`
}

func ListTags[T *GogsTag](
	c *GogsClient,
	owner,
	repo string,
) dp.Pager[T] {
	resStrFmt := "/repos/%s/%s/tags"
	resStr := fmt.Sprintf(
		resStrFmt,
		url.PathEscape(owner),
		url.PathEscape(repo),
	)
	resource, err := url.Parse(resStr)
	if err != nil {
		panic(err)
	}
	return dp.NewPager[T](
		newGogsSubclient[T](c, resource),
		100,
	)
}

type GogsArchive struct {
	Contents []byte
}

func DownloadArchive[T *GogsArchive](
	c *GogsClient,
	owner,
	repo,
	ref string,
) (*GogsArchive, error) {
	resStrFmt := "/repos/%s/%s/archive/%s%s"
	resStr := fmt.Sprintf(
		resStrFmt,
		url.PathEscape(owner),
		url.PathEscape(repo),
		url.PathEscape(ref),
		url.PathEscape(".zip"),
	)
	resource, err := url.Parse(resStr)
	if err != nil {
		panic(err)
	}
	expanded := c.expandResource(resource)
	_, body, err := c.get(expanded)
	if err != nil {
		return nil, fmt.Errorf("download gogs archive: %v", err)
	}
	return &GogsArchive{Contents: body}, nil
}