package gomod

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"

	"git.yetaga.in/alazyreader/libyear/pkg/cache"
	"git.yetaga.in/alazyreader/libyear/pkg/libyear"
)

// A Queryer holds settings for a
type Queryer struct {
	Root   string
	Client http.Client
	Cache  cache.Cache
	Logger logger
}

type majorVersion struct {
	raw     string
	version int
}

// GetLatestVersion returns the "latest" major version of a module,
// jumping across MVS boundaries:
// i.e. github.com/foo/bar => github.com/foo/bar/v2 in the case of one version bump
// github.com/foo/baz/v2 => github.com/foo/baz/v6 in the case of a large jump
// github.com/foo/quuz/v2 => github.com/foo/quuz/v2 in the case of no jump at all.
func (q *Queryer) GetLatestVersion(module string) libyear.Info {
	latestMod := q.findLatestMajorVersion(module)
	return q.makeProxyRequest(latestMod + "/@latest")
}

// GetVersion returns the proxy's information about a given version of a module.
// `module` in this case is a fully-disambiguated MVS name (github.com/foo/bar/v2),
// and `version` is a version identifier as defined in `https://blog.golang.org/publishing-go-modules#TOC_3.`
func (q *Queryer) GetVersion(module string, version string) libyear.Info {
	if !strings.HasPrefix(version, "v") {
		return libyear.Info{
			Version: version,
		}
	}
	i := q.makeProxyRequest(module + "/@v/" + version + ".info")
	if i.Version == "" {
		i.Version = version
	}
	return i
}

// given a module, return the "latest" major version of that module, fully defined
func (q *Queryer) findLatestMajorVersion(module string) string {
	for {
		nextModule := incrementMajorVersion(module)
		info := q.makeProxyRequest(nextModule + "/@latest")
		if info.Version == "" {
			return module
		}
		module = nextModule
	}
}

// handle calling the go module proxy
func (q *Queryer) makeProxyRequest(mod string) libyear.Info {
	if q.Root == "" {
		q.Root = "https://proxy.golang.org/"
	}
	q.Logger.Debugf("makeProxyRequest for %s/%s\n", q.Root, mod)

	u, _ := url.Parse(q.Root)
	u.Path = mod

	i := q.Cache.Get(u.String())
	if i.Version != "" {
		q.Logger.Debugf("cache hit for https://proxy.golang.org/%s\n", mod)
		return i
	}
	req, err := http.NewRequest("GET", u.String(), nil)
	if err != nil {
		return i
	}
	req.Header.Add("Disable-Module-Fetch", "true")
	resp, err := q.Client.Do(req)
	if err != nil || resp.StatusCode != 200 {
		return i
	}
	b, _ := io.ReadAll(resp.Body)
	err = json.Unmarshal(b, &i)
	q.Cache.Set(u.String(), i)
	return i
}

// parses and attempts to add an MVS version to a module
func incrementMajorVersion(mod string) string {
	exp := strings.Split(mod, "/")
	var module string
	if exp[len(exp)-1][0] == 'v' {
		n, err := strconv.Atoi(exp[len(exp)-1][1:])
		if err != nil {
			module = mod + "/v2"
		} else {
			module = strings.Join(exp[:len(exp)-1], "/") + "/v" + fmt.Sprint(n+1)
		}
	} else {
		module = mod + "/v2"
	}
	return module
}