package gomod

import (
	"os"

	"git.yetaga.in/alazyreader/libyear/pkg/libyear"
	"golang.org/x/mod/modfile"
)

// GoMod represents a Go Modules parser.
// Running LoadAndComputePairs with a filename will return a slice of parsed dependencies.
type GoMod struct {
	IncludeIndirect bool
	ProxyLoader     Queryer
	Logger          logger
}

// logger is an extremely simple leveled logger
type logger interface {
	Logf(f string, s ...interface{})
	Debugf(f string, s ...interface{})
}

// LoadAndComputePairs takes a filename of a go.mod file,
// runs the resolution algorithm in the provided Querier,
// and returns parsed pairs of dependencies and their latest versions.
func (g *GoMod) LoadAndComputePairs(filename string) ([]libyear.Pair, error) {
	b, err := os.ReadFile(filename)
	if err != nil {
		return nil, err
	}
	f, err := modfile.Parse(filename, b, nil)
	if err != nil {
		return nil, err
	}
	pairs := []libyear.Pair{}

	for v := range f.Require {
		if f.Require[v].Mod.Path != "" && f.Require[v].Mod.Version != "" {
			if isReplaced(f.Require[v].Mod.Path, f.Replace) {
				g.Logger.Logf("%s is replaced, skipping...\n", f.Require[v].Mod.Path)
				continue
			}
			if !g.IncludeIndirect && f.Require[v].Indirect {
				g.Logger.Logf("%s is indirect, skipping...\n", f.Require[v].Mod.Path)
				continue
			}
			latest := g.ProxyLoader.GetLatestVersion(f.Require[v].Mod.Path)
			current := g.ProxyLoader.GetVersion(f.Require[v].Mod.Path, f.Require[v].Mod.Version)
			pairs = append(pairs, libyear.Pair{
				Name:    f.Require[v].Mod.Path,
				Current: current,
				Latest:  latest,
			})
		}
	}
	return pairs, nil
}

func isReplaced(module string, replaces []*modfile.Replace) bool {
	for i := range replaces {
		if module == replaces[i].Old.Path {
			return true
		}
	}
	return false
}