package goldsmith

import (
	"os"
	"path/filepath"
	"sync"
)

type goldsmith struct {
	srcDir, dstDir string
	contexts       []*context
	refs           map[string]bool
	complete       bool
	filters        []Filter

	errors   []error
	errorMtx sync.Mutex
}

func (gs *goldsmith) pushContext(plug Plugin) *context {
	ctx := &context{gs: gs, plug: plug, output: make(chan *file)}
	ctx.filters = append(ctx.filters, gs.filters...)

	if len(gs.contexts) > 0 {
		ctx.input = gs.contexts[len(gs.contexts)-1].output
	}

	gs.contexts = append(gs.contexts, ctx)
	return ctx
}

func (gs *goldsmith) cleanupFiles() {
	infos := make(chan fileInfo)
	go scanDir(gs.dstDir, infos)

	for info := range infos {
		relPath, _ := filepath.Rel(gs.dstDir, info.path)
		if contained, _ := gs.refs[relPath]; contained {
			continue
		}

		os.RemoveAll(info.path)
	}
}

func (gs *goldsmith) exportFile(f *file) error {
	if err := f.export(gs.dstDir); err != nil {
		return err
	}

	pathSeg := cleanPath(f.path)
	for {
		gs.refs[pathSeg] = true
		if pathSeg == "." {
			break
		}

		pathSeg = filepath.Dir(pathSeg)
	}

	return nil
}

func (gs *goldsmith) fault(name string, f *file, err error) {
	gs.errorMtx.Lock()
	defer gs.errorMtx.Unlock()

	ferr := &Error{Name: name, Err: err}
	if f != nil {
		ferr.Path = f.path
	}

	gs.errors = append(gs.errors, ferr)
}

//
//	Goldsmith Implementation
//

func (gs *goldsmith) Chain(p Plugin) Goldsmith {
	if gs.complete {
		panic("attempted reuse of goldsmith instance")
	}

	gs.pushContext(p)
	return gs
}

func (gs *goldsmith) FilterPush(f Filter) Goldsmith {
	if gs.complete {
		panic("attempted reuse of goldsmith instance")
	}

	gs.filters = append(gs.filters, f)
	return gs
}

func (gs *goldsmith) FilterPop() Goldsmith {
	if gs.complete {
		panic("attempted reuse of goldsmith instance")
	}

	count := len(gs.filters)
	if count == 0 {
		panic("attempted to pop empty filter stack")
	}

	gs.filters = gs.filters[:count-1]
	return gs
}

func (gs *goldsmith) End(dstDir string) []error {
	if gs.complete {
		panic("attempted reuse of goldsmith instance")
	}

	gs.dstDir = dstDir

	for _, ctx := range gs.contexts {
		go ctx.step()
	}

	ctx := gs.contexts[len(gs.contexts)-1]
	for f := range ctx.output {
		gs.exportFile(f)
	}

	gs.cleanupFiles()
	gs.complete = true

	return gs.errors
}