package syw

import (
	"bytes"
	"context"
	"mime"
	"os"
	"path"
	"path/filepath"
	"strings"
	"text/template"

	"tildegit.org/tjp/sliderule"
	"tildegit.org/tjp/sliderule/spartan"
)

// SpartanRouter builds a router that will handle requests into a directory of git repositories.
//
// The routes it defines are:
//
//	/                                     gemtext listing of the repositories in the directory
//	/:repository/                         gemtext overview of the repository
//	/:repository/branches                 gemtext list of branches/heads
//	/:repository/tags                     gemtext listing of tags
//	/:repository/refs/:ref/               gemtext overview of a ref
//	/:repository/refs/:ref/tree/*path     gemtext listing of directories, raw files
//	/:repository/diffstat/:fromref/:toref text/plain diffstat between two refs
//	/:repository/diff/:fromref/:toref     text/x-diff between two refs
//
// The overrides argument can provide templates to define the behavior of nearly all of the above
// routes. All of them have default implementations so the argument can even be nil, but otherwise
// the template names used are:
//
//	repo_root.gmi    gemtext at /
//	repo_home.gmi    gemtext at /:repository/
//	branch_list.gmi  gemtext at /:repository/branches
//	tag_list.gmi     gemtext at /:repository/tags
//	ref.gmi          gemtext at /:repository/refs/:ref/
//	tree.gmi         gemtext for directories requested under /:repository/refs/:ref/tree/*path
//	                 (file paths return the raw files without any template involved)
//	diffstat.gmi.txt the plaintext diffstat at /:repository/diffstat/:fromref/:toref
//	diff.gmi.txt     the text/x-diff at /:repository/diff/:fromref/:toref
//
// Most of the templates above are rendered with an object with 3 fields:
//
//	Ctx:    the context.Context from the request
//	Repo:   a *syw.Repository object corresponding to <repodir>/:repository
//	Params: a map[string]string of the route parameters
//
// The only exception is repo_root.gmi, which is rendered with a slice of the repo names instead.
func SpartanRouter(repodir string, overrides *template.Template) *sliderule.Router {
	tmpl, err := addTemplates(geminiTemplate, overrides)
	if err != nil {
		panic(err)
	}

	repoRouter := &sliderule.Router{}
	repoRouter.Use(assignRepo(repodir))
	repoRouter.Route("/", sgmiTemplate(tmpl, "repo_home.gmi"))
	repoRouter.Route("/branches", sgmiTemplate(tmpl, "branch_list.gmi"))
	repoRouter.Route("/tags", sgmiTemplate(tmpl, "tag_list.gmi"))
	repoRouter.Route("/refs/:ref/", sgmiTemplate(tmpl, "ref.gmi"))
	repoRouter.Route("/refs/:ref/tree/*path", spartanTreePath(tmpl))
	repoRouter.Route("/diffstat/:fromref/:toref", runSpartanTemplate(tmpl, "diffstat.gmi.txt", "text/plain"))
	repoRouter.Route("/diff/:fromref/:toref", runSpartanTemplate(tmpl, "diff.gmi.txt", "text/x-diff"))

	router := &sliderule.Router{}
	router.Route("/", spartanRoot(repodir, tmpl))
	router.Mount("/:"+reponamekey, repoRouter)

	return router
}

func spartanRoot(repodir string, tmpl *template.Template) sliderule.Handler {
	return sliderule.HandlerFunc(func(ctx context.Context, request *sliderule.Request) *sliderule.Response {
		entries, err := os.ReadDir(repodir)
		if err != nil {
			return spartan.ServerError(err)
		}

		names := []string{}
		for _, item := range entries {
			if Open(filepath.Join(repodir, item.Name())) != nil {
				names = append(names, item.Name())
			}
		}

		buf := &bytes.Buffer{}
		if err := tmpl.ExecuteTemplate(buf, "repo_root.gmi", names); err != nil {
			return spartan.ServerError(err)
		}

		return spartan.Success("text/gemini; charset=utf-8", buf)
	})
}

func spartanTreePath(tmpl *template.Template) sliderule.Handler {
	return sliderule.HandlerFunc(func(ctx context.Context, request *sliderule.Request) *sliderule.Response {
		params := sliderule.RouteParams(ctx)
		if params["path"] == "" || strings.HasSuffix(params["path"], "/") {
			return sgmiTemplate(tmpl, "tree.gmi").Handle(ctx, request)
		}

		repo := ctx.Value(repokey).(*Repository)

		body, err := repo.Blob(ctx, params["ref"], params["path"])
		if err != nil {
			return spartan.ServerError(err)
		}

		mediaType := ""
		ext := path.Ext(params["path"])
		if ext == ".gmi" {
			mediaType = "text/gemini; charset=utf-8"
		} else {
			mediaType = mime.TypeByExtension(ext)
		}
		if mediaType == "" {
			mediaType = "application/octet-stream"
		}

		return spartan.Success(mediaType, bytes.NewBuffer(body))
	})
}

func sgmiTemplate(tmpl *template.Template, name string) sliderule.Handler {
	return runSpartanTemplate(tmpl, name, "text/gemini; charset=utf-8")
}

func runSpartanTemplate(tmpl *template.Template, name, mimetype string) sliderule.Handler {
	return sliderule.HandlerFunc(func(ctx context.Context, request *sliderule.Request) *sliderule.Response {
		obj := map[string]any{
			"Ctx":    ctx,
			"Repo":   ctx.Value(repokey),
			"Params": sliderule.RouteParams(ctx),
		}
		buf := &bytes.Buffer{}

		if err := tmpl.ExecuteTemplate(buf, name, obj); err != nil {
			return spartan.ServerError(err)
		}

		return spartan.Success(mimetype, buf)
	})
}