// This module defines the Context type, which carries deadlines, cancellation signals,
// and other request-scoped values across API boundaries and between processes.
// Based on:   https://github.com/golang/go/tree/master/src/context
// Last commit: https://github.com/golang/go/commit/52bf14e0e8bdcd73f1ddfb0c4a1d0200097d3ba2
module context

import time

// A ValueContext carries a key-value pair. It implements Value for that key and
// delegates all other calls to the embedded Context.
pub struct ValueContext {
    key   Key
    value Any
mut:
    context Context
}

// with_value returns a copy of parent in which the value associated with key is
// val.
//
// Use context Values only for request-scoped data that transits processes and
// APIs, not for passing optional parameters to functions.
//
// The provided key must be comparable and should not be of type
// string or any other built-in type to avoid collisions between
// packages using context. Users of with_value should define their own
// types for keys
pub fn with_value(parent Context, key Key, value Any) Context {
    return &ValueContext{
        context: parent
        key:     key
        value:   value
    }
}

// deadline returns the deadline from the parent context.
pub fn (ctx &ValueContext) deadline() ?time.Time {
    return ctx.context.deadline()
}

// done returns the done channel from the parent context.
pub fn (mut ctx ValueContext) done() chan int {
    return ctx.context.done()
}

// err returns the error from the parent context.
pub fn (mut ctx ValueContext) err() IError {
    return ctx.context.err()
}

// value returns the value associated with this context for the given key.
// If the key matches the one stored in this ValueContext, its value is returned.
// Otherwise, the lookup is delegated to the parent context.
pub fn (ctx &ValueContext) value(key Key) ?Any {
    if ctx.key == key {
        return ctx.value
    }
    return ctx.context.value(key)
}

// str returns a string representation of the ValueContext,
// showing the parent context name suffixed with '.with_value'.
pub fn (ctx &ValueContext) str() string {
    return context_name(ctx.context) + '.with_value'
}