github.com/altoros/juju-vmware@v0.0.0-20150312064031-f19ae857ccca/upgrades/contexts.go (about)

     1  // Copyright 2014 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package upgrades
     5  
     6  import (
     7  	"github.com/juju/juju/agent"
     8  	"github.com/juju/juju/api"
     9  	"github.com/juju/juju/state"
    10  )
    11  
    12  // Context provides the dependencies used when executing upgrade steps.
    13  type Context interface {
    14  	// APIState returns an API connection to state.
    15  	APIState() *api.State
    16  
    17  	// State returns a connection to state. This will be non-nil
    18  	// only in the context of a state server.
    19  	State() *state.State
    20  
    21  	// AgentConfig returns the agent config for the machine that is being
    22  	// upgraded.
    23  	AgentConfig() agent.ConfigSetter
    24  
    25  	// StateContext returns a new Context suitable for State-based
    26  	// upgrade steps.
    27  	StateContext() Context
    28  
    29  	// APIContext returns a new Context suitable for API-based upgrade
    30  	// steps.
    31  	APIContext() Context
    32  }
    33  
    34  // NewContext returns a new upgrade context.
    35  func NewContext(agentConfig agent.ConfigSetter, api *api.State, st *state.State) Context {
    36  	return &upgradeContext{
    37  		agentConfig: agentConfig,
    38  		api:         api,
    39  		st:          st,
    40  	}
    41  }
    42  
    43  // upgradeContext is a default Context implementation.
    44  type upgradeContext struct {
    45  	agentConfig agent.ConfigSetter
    46  	api         *api.State
    47  	st          *state.State
    48  }
    49  
    50  // APIState is defined on the Context interface.
    51  //
    52  // This will panic if called on a Context returned by StateContext.
    53  func (c *upgradeContext) APIState() *api.State {
    54  	if c.api == nil {
    55  		panic("API not available from this context")
    56  	}
    57  	return c.api
    58  }
    59  
    60  // State is defined on the Context interface.
    61  //
    62  // This will panic if called on a Context returned by APIContext.
    63  func (c *upgradeContext) State() *state.State {
    64  	if c.st == nil {
    65  		panic("State not available from this context")
    66  	}
    67  	return c.st
    68  }
    69  
    70  // AgentConfig is defined on the Context interface.
    71  func (c *upgradeContext) AgentConfig() agent.ConfigSetter {
    72  	return c.agentConfig
    73  }
    74  
    75  // StateContext is defined on the Context interface.
    76  func (c *upgradeContext) StateContext() Context {
    77  	return &upgradeContext{
    78  		agentConfig: c.agentConfig,
    79  		st:          c.st,
    80  	}
    81  }
    82  
    83  // APIContext is defined on the Context interface.
    84  func (c *upgradeContext) APIContext() Context {
    85  	return &upgradeContext{
    86  		agentConfig: c.agentConfig,
    87  		api:         c.api,
    88  	}
    89  }