package rules

import (
	"fmt"
	"go/ast"
	"go/token"
	"strings"
)

func init() {
	registered = append(registered,
		Rule{
			ID:       "wire.hook-bad-signature",
			Severity: SeverityWarning,
			Module:   "wire",
			Check:    checkHookSignature,
		},
		Rule{
			ID:       "wire.hook-outside-beforestart",
			Severity: SeverityWarning,
			Module:   "wire",
			Check:    checkHookBodyShape,
		},
		Rule{
			ID:       "wire.route-specific-after-param",
			Severity: SeverityWarning,
			Module:   "web",
			Check:    checkRouteOrdering,
		},
	)
}

// isHookName reports whether name matches the with<Feature> convention.
// A hook is "with" + capital letter + anything, so "with" and "withers"
// don't qualify but "withUsers", "withAuth", "withSuperAdminSeed" do.
func isHookName(name string) bool {
	if len(name) < 5 || !strings.HasPrefix(name, "with") {
		return false
	}
	c := name[4]
	return c >= 'A' && c <= 'Z'
}

func checkHookSignature(c *Context) []Finding {
	var findings []Finding
	for _, decl := range c.File.Decls {
		fn, ok := decl.(*ast.FuncDecl)
		if !ok || fn.Recv != nil || !isHookName(fn.Name.Name) {
			continue
		}
		params := fn.Type.Params
		if params == nil || len(params.List) == 0 {
			findings = append(findings, Finding{
				Message: fmt.Sprintf("hook %s has no parameters; expected first param launcher.Launcher", fn.Name.Name),
				Hint:    "func with<Feature>(lc launcher.Launcher, srv server.Server, deps...)",
				Line:    c.Fset.Position(fn.Pos()).Line,
			})
			continue
		}
		first := exprName(params.List[0].Type)
		if !strings.Contains(first, "Launcher") {
			findings = append(findings, Finding{
				Message: fmt.Sprintf("hook %s first param is %q; expected launcher.Launcher", fn.Name.Name, first),
				Hint:    "Always pass the launcher as the first argument so the hook can register BeforeStart.",
				Line:    c.Fset.Position(fn.Pos()).Line,
			})
		}
	}
	return findings
}

func checkHookBodyShape(c *Context) []Finding {
	var findings []Finding
	for _, decl := range c.File.Decls {
		fn, ok := decl.(*ast.FuncDecl)
		if !ok || fn.Recv != nil || fn.Body == nil || !isHookName(fn.Name.Name) {
			continue
		}
		for _, stmt := range fn.Body.List {
			if !suspiciousTopLevelStmt(stmt) {
				continue
			}
			findings = append(findings, Finding{
				Message: fmt.Sprintf("hook %s performs wiring outside lc.BeforeStart", fn.Name.Name),
				Hint:    "Move repo/service/handler construction and route registration inside lc.BeforeStart(func() error { ... return nil }).",
				Line:    c.Fset.Position(stmt.Pos()).Line,
			})
		}
	}
	return findings
}

// suspiciousTopLevelStmt is true for top-level statements inside a hook that
// look like wiring work (route registration or component construction) but
// are not the canonical lc.BeforeStart or lc.Append calls.
func suspiciousTopLevelStmt(stmt ast.Stmt) bool {
	if expr, ok := stmt.(*ast.ExprStmt); ok {
		if call, ok := expr.X.(*ast.CallExpr); ok {
			name := exprName(call.Fun)
			if strings.HasSuffix(name, ".BeforeStart") ||
				strings.HasSuffix(name, ".Append") ||
				strings.HasSuffix(name, ".Run") {
				return false
			}
		}
	}
	suspicious := false
	ast.Inspect(stmt, func(n ast.Node) bool {
		call, ok := n.(*ast.CallExpr)
		if !ok {
			return true
		}
		name := exprName(call.Fun)
		switch {
		case strings.HasSuffix(name, ".Get"),
			strings.HasSuffix(name, ".Post"),
			strings.HasSuffix(name, ".Put"),
			strings.HasSuffix(name, ".Patch"),
			strings.HasSuffix(name, ".Delete"),
			strings.HasSuffix(name, ".New"):
			suspicious = true
			return false
		}
		return true
	})
	return suspicious
}

type routeReg struct {
	method string
	path   string
	pos    token.Pos
}

func collectRoutes(file *ast.File) []routeReg {
	var routes []routeReg
	ast.Inspect(file, func(n ast.Node) bool {
		call, ok := n.(*ast.CallExpr)
		if !ok {
			return true
		}
		sel, ok := call.Fun.(*ast.SelectorExpr)
		if !ok {
			return true
		}
		switch sel.Sel.Name {
		case "Get", "Post", "Put", "Patch", "Delete":
		default:
			return true
		}
		if len(call.Args) < 1 {
			return true
		}
		lit, ok := call.Args[0].(*ast.BasicLit)
		if !ok || lit.Kind != token.STRING {
			return true
		}
		routes = append(routes, routeReg{
			method: sel.Sel.Name,
			path:   strings.Trim(lit.Value, `"`),
			pos:    call.Pos(),
		})
		return true
	})
	return routes
}

func checkRouteOrdering(c *Context) []Finding {
	routes := collectRoutes(c.File)
	var findings []Finding
	for i := 0; i < len(routes); i++ {
		for j := i + 1; j < len(routes); j++ {
			if routes[i].method != routes[j].method {
				continue
			}
			if !routesConflict(routes[i].path, routes[j].path) {
				continue
			}
			findings = append(findings, Finding{
				Message: fmt.Sprintf("%s %s registered before %s %s — chi will bind %q to a path parameter and the literal route becomes unreachable",
					routes[i].method, routes[i].path,
					routes[j].method, routes[j].path,
					conflictingSegment(routes[i].path, routes[j].path),
				),
				Hint: "Register literal-segment routes before parametrised siblings that share the same prefix.",
				Line: c.Fset.Position(routes[i].pos).Line,
			})
		}
	}
	return findings
}

// routesConflict reports whether `param` is a parametrised route that would
// shadow `literal` (a route differing only in one segment being a literal
// where param has {placeholder}).
func routesConflict(param, literal string) bool {
	p := strings.Split(strings.Trim(param, "/"), "/")
	l := strings.Split(strings.Trim(literal, "/"), "/")
	if len(p) != len(l) {
		return false
	}
	hasParam := false
	for i := range p {
		pIsParam := isParamSeg(p[i])
		lIsParam := isParamSeg(l[i])
		if pIsParam {
			if lIsParam {
				return false
			}
			hasParam = true
			continue
		}
		if p[i] != l[i] {
			return false
		}
	}
	return hasParam
}

func isParamSeg(s string) bool {
	return strings.HasPrefix(s, "{") && strings.HasSuffix(s, "}")
}

func conflictingSegment(param, literal string) string {
	p := strings.Split(strings.Trim(param, "/"), "/")
	l := strings.Split(strings.Trim(literal, "/"), "/")
	for i := range p {
		if isParamSeg(p[i]) && !isParamSeg(l[i]) {
			return l[i]
		}
	}
	return ""
}